Folio

A fast, clean PDF reader for Windows, macOS, and Linux. Read, highlight, annotate, sign, and ask AI about your documents. Free and open source, with no Folio account required.

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Download

Platform	Download	Updates
Windows 10/11 (64-bit)	Folio-Setup.exe	Automatic
macOS 12 or later (Apple Silicon and Intel)	Folio-mac.dmg	Folio tells you when a new version is out
Linux: Ubuntu, Debian, and derivatives (64-bit)	Folio-linux-amd64.deb	Automatic, with your system updates (apt)
Linux: other distributions (64-bit)	Folio-linux-x86_64.AppImage	Automatic

All releases · Changelog · Prefer not to install on Windows? Folio-Portable.exe on the release page runs as-is (it doesn't auto-update).

Folio's builds aren't signed with paid developer certificates yet, so the first launch needs one extra step:

• Windows: if SmartScreen warns, choose More info → Run anyway.
• macOS: open the DMG and drag Folio to Applications. The first time you open it, macOS says it can't verify the developer: click Done, then go to System Settings → Privacy & Security and click Open Anyway.
• Linux (.deb): sudo apt install ./Folio-linux-amd64.deb, then open Folio from your applications menu. The package adds Folio's signed apt repository, so new versions arrive with your regular system updates (or sudo apt update && sudo apt upgrade). Copies installed from a .deb before 1.9 need the new .deb installed once.
• Linux (AppImage): make it executable (chmod +x Folio-linux-x86_64.AppImage) and run it. AppImages need FUSE 2: sudo apt install libfuse2t64 on Ubuntu 24.04 or later, libfuse2 on older releases.

Or build Folio yourself from source (below).

Features

Open PDFs and web links

• Document tabs. Pick or drop several PDFs together, or choose More → New tab. The tab strip appears beneath the toolbar when two or more tabs are open. Each document keeps its page, zoom, and edits when you switch.
• PDF URLs: choose Open from URL (Ctrl+Shift+O), or drop a link or paste it with Ctrl+V outside a text field to fill it in, then press Open. Folio downloads and opens the PDF, follows redirects, and uses the server's filename when available. Folio asks once more before opening an address on your computer or local network.
• Webpage to PDF: use the same URL workflow for a webpage. Folio converts it into a PDF with selectable text, ready for highlights, notes, and Ask AI. The conversion preserves the site's on-screen layout, backgrounds, transparency, colors, and images instead of switching to its print styles.
• Word documents to PDF: open a .docx or .doc file the same ways as a PDF (Open with → Folio, the file picker, or drag and drop). Folio opens the PDF and saves a private copy beside the original when possible ("Report.docx" gets "Report.pdf"). Occupied names get a number. Reopening reuses a copy only if both files still match Folio's conversion record. Opening a symbolic link, or a file on a separate volume on macOS, skips the automatic save. Folio converts with Microsoft Word on Windows when it's installed, otherwise with LibreOffice, otherwise with its own converter for .docx (text, headings, lists, tables, and images, in a simpler layout). .doc files need Word or LibreOffice, except on macOS. Installing Folio adds it to Open with for Word documents without making it their default app.
• Password-protected PDFs: enter the password to read and annotate a protected document. These documents are not kept in the recent library, and their annotations and AI conversations are not persisted locally between sessions.
• Sample document: try the built-in tour from the home screen without finding a PDF first.

URL opening, webpage conversion, and Word conversion require the desktop app. Failed downloads leave your current document open.

Read and navigate

• Back and Forward: after following an internal link or an outline entry, choose More → Back to return to your place. The first jump also shows a brief, clickable Back hint. More → Forward appears after you go back. Each tab remembers its own positions, zoom, and rotation until the document closes. Use Alt+← / Alt+→ (⌥← / ⌥→ on macOS) while reading. Text fields and dialogs keep their normal editing controls.
• Continuous scrolling with selectable text, previous/next controls, and a page-number field for jumping directly to a page. Enable Settings → Reading → Scroll one page at a time to turn pages with the mouse wheel.
• Pages and Outline tabs: browse page thumbnails or the PDF's existing outline/bookmarks; hide the sidebar when you want more reading space.
• Personal bookmarks: click the ribbon beside a page number in Pages to save or remove a bookmark without leaving your current page. Turn on Bookmarked at the top of the sidebar to see just your saved pages, then select a thumbnail to jump to it. These bookmarks are included in Markdown and JSON exports. Folio remembers them locally when you reopen a PDF, except for password-protected documents.
• Reorder pages from either sidebar tab. Drag thumbnails or enter a new position, then save and open the reordered PDF copy.
• Export selected pages from the Pages sidebar. Ctrl-click thumbnails (⌘-click on macOS) to select individual pages, or Shift-click for a range. Right-click a selected thumbnail to save those pages in document order as a new PDF.
• Search as you type: match case or whole words, see the current match and total count, browse per-page snippets and match counts, and move between matches with Enter / Shift+Enter.
• Flexible views: fit to width, fit to page, automatic sizing, preset zoom levels, zoom buttons, Ctrl+wheel / trackpad pinch, two-page spreads, and page rotation.
• Focus mode: press F for distraction-free, fullscreen reading; press Esc to return.
• Light and dark themes, plus an independent ⋯ → PDF dark mode setting that dims bright pages while keeping photos and figures in their original colors, including in thumbnails. Both settings survive restarts.

Edit existing text and images

Choose Edit mode, then click the text you want to change and type on the page. Press Enter or click outside the line to apply it. Esc cancels typing. Clear a line to delete it.

Click an embedded picture and choose Replace image… to select a PNG or JPEG. You can leave Edit mode to read your changes or use Save copy to export and open the edited PDF.

Open More → Version history to review your changes. Saving a changed copy keeps the original PDF and a numbered version on this device. Text edits show the old and new wording, and image replacements show the filename and page. Open or download an earlier version from the panel. History is available for unencrypted PDFs up to 50 MB and can be cleared per document.

Text keeps its original font and position. Longer replacements can overlap neighboring content, so check the page after applying a change. Only characters available in that font can be used. Scanned words, outlined lettering, and objects inside grouped artwork cannot be edited as text. Image replacement supports embedded image objects on pages without inline image data. The editor works with unsigned, unencrypted PDFs.

Highlight, draw, and take notes

• Select text in scans. Folio recognizes English by default. In Settings → Reading → Scan languages, search for a language by its English or local name. Select the languages in your document. The dropdown shows the total size of any packs to download. Folio keeps them on this device for offline use and re-reads open scans. The page you jump to gets priority. A message above the page controls shows when text is still being prepared. Once it clears, drag across the words to copy, highlight, or ask about a passage. Recognition runs offline.
• One-click highlights: select text, then choose yellow, green, blue, pink, or red from the selection toolbar; H applies the current highlight color.
• Choose Highlight in the toolbar to mark each passage in the current color as soon as you select it. Choose Done or press Esc to return to reading.
• Notes on passages: type into the selection toolbar and press Enter to highlight with a note, or press N with text selected to focus the note box.
• Edit existing highlights: click one to recolor it, edit its note, ask AI about the passage, or remove it.
• Draw on a page: choose Draw (D) for a freehand pen, rectangle, oval, or arrow. With Pen selected, choose Thin, Medium, or Thick for your next strokes. Pick a color, then drag on the page. Drawings can be undone and are included when you save a PDF copy.
• Text boxes: choose Text (T) to add text to a page, using the same ink palette.
• Undo and redo annotation edits with the usual keyboard shortcuts; choose Done, V, or Esc to leave a drawing/text tool and return to selection.
• Notes tab: review highlights, their notes, and text boxes; click an entry to jump to it, edit a highlight's note, delete an entry, or ask AI about a highlight. A separate notes box holds thoughts about the whole document.
• Export reading notes: in Notes → Export, copy Markdown or save a JSON file. JSON includes your notes, highlights, text boxes, drawings and shapes with one-based page numbers, plus the PDF's outline bookmarks. It includes stable annotation IDs, colors, and coordinates in unrotated PDF user space for use in other tools.
• Automatic local saving: highlights, notes, drawings, and text boxes return when you reopen an ordinary, non-password-protected PDF. Use Save a copy to share page annotations with other readers.

Add handwritten signatures

Choose Sign in the toolbar to add a signature.

• Capture on paper: sign with dark ink on white paper, then use your camera or upload a PNG, JPEG, or WebP photo.
• Clean up the image: crop to the signature and adjust ink sensitivity to remove the paper background. Capture and image processing stay on your device.
• Suggested placement: Folio checks the current page for empty PDF signature fields and likely signature labels, then offers places to sign. Detection is a suggestion, not a guarantee that every field will be found.
• Preview and position: review the actual page, pick a suggestion or place the signature manually, and adjust its width before approving.
• Explicit approval: nothing is added until you click Approve and add signature. Signatures are visual stamps, not certificate-based digital signatures. Use Save a copy to keep a signed PDF; placed signatures are not part of Folio's automatic annotation restoration.
• Optional reuse: choose to remember a signature on this computer; remove the saved image in Settings → Signature → Forget.

Ask AI about a document

• Choose a provider: use your ChatGPT plan, your Claude subscription through Claude Code, or your own OpenRouter API key.
• Whole-document or passage questions: open the Ask AI panel from the toolbar, select text and choose Ask AI, or ask about an existing highlight.
• Streaming answers with clickable page citations that jump back to the source page.
• Copy response copies a finished AI answer with its Markdown formatting and page citations.
• Rendered mathematics: inline and display LaTeX equations, with wide equations scrolling within the chat panel. Supports \( ... \), \[ ... \], $x$, and $$ ... $$; existing saved answers render too.
• Provider and model selection, a stop button for an in-progress answer, and a + button to start a fresh conversation.
• Per-document history: conversations are saved on this computer and restored when you reopen that document, except for password-protected PDFs. Starting a new conversation clears that document's saved chat. Open Settings → Storage → Stored data to see how many documents have saved annotations or chats, including documents removed from Recent. You can clear either category separately. Annotations include document notes and bookmarks.
• Account settings: choose your default provider, sign in to or out of ChatGPT, and check Claude Code's connection from Settings → Ask AI.

Ask AI is optional and desktop-only. See Using Ask AI for setup and Privacy for what is sent.

Inspect images

• Click a PDF image and choose View larger for a high-resolution, full-window view.
• Switch between Fit to window and Actual size, or copy the image to your clipboard.
• Choose Open in browser when an image has a web address. Images in converted webpages retain their original image links.

Pick up where you left off

• Recent library: keep up to eight recently opened PDFs with thumbnail previews and the last page read; reopen with one click, remove individual entries, or choose Clear all.
• Startup restore: reopen the last active document automatically when it is still in the recent library.
• Reading state: remember each document's page, scroll position, zoom, rotation, sidebar visibility, and two-page mode.
• Window state: restore the desktop window's size, monitor position, and maximized state.

Save, print, and inspect

• Save a copy (Ctrl+S) exports a PDF with page annotations, including highlights and attached notes, drawings, text boxes, and visual signatures. Your original file is not overwritten. Whole-document notes and AI chat history stay in Folio; copy notes as Markdown when you want to share them.
• Print (Ctrl+P, or ⌘P on macOS) previews each page at its own proportions and prints the annotated PDF. On desktop, choose Advanced for poster, booklet, or multiple pages per sheet.
• Document info shows available metadata: filename, title, author, subject, page count and size, file size, creation/modification dates, generating application, producer, and PDF version.

Settings and updates

Open ⋯ → Settings or press Ctrl+, for appearance, night reading, AI accounts and defaults, remembered signatures, and updates. About Folio shows the version, installed/portable edition, and installation location, with a shortcut to open that folder.

• Automatic updates on or off: the preference survives restarts. Turning it off stops background checks/downloads and automatic installation; manual Check for updates remains available for self-updating editions.
• Installed Windows: updates download in the background and install silently on exit, or when you choose Restart and update, without repeating the Setup wizard.
• Linux AppImage: downloads updates and replaces the AppImage. Linux .deb: updates through the signed apt repository and your system updater; Folio's toggle does not disable apt updates.
• macOS: current unsigned builds notify you and offer the download; self-installing updates require a signed build. Windows portable: download a replacement manually.
• Visible update status: checking, download progress, update-ready prompts, and errors are shown in the app.

Keyboard shortcuts

On macOS, use ⌘ wherever this table says Ctrl. Press ? with a document open for in-app help.

Action	Shortcut
Open a PDF / open a URL	Ctrl+O / Ctrl+Shift+O
New tab / close tab	Ctrl+T / Ctrl+W
Next tab / previous tab (Control on all platforms)	Control+Tab / Control+Shift+Tab
Find / next match / previous match	Ctrl+F / Enter / Shift+Enter
Back / forward through links	Alt+← / Alt+→ (⌥← / ⌥→ on macOS)
Highlight selection or enter Highlight mode / write a note	H / N
Remove a clicked highlight	Delete
Select / draw / add text	V / D / T
Undo / redo annotation edits	Ctrl+Z / Ctrl+Shift+Z or Ctrl+Y
Save a copy / print	Ctrl+S / Ctrl+P
Zoom in / zoom out / reset zoom	Ctrl++ / Ctrl+- / Ctrl+0
Toggle sidebar	Ctrl+\
Rotate / toggle two-page view	R / 2
First page / last page	Home / End
Focus mode / leave focus or current tool	F / Esc
Settings / keyboard help	Ctrl+, / ?

Current limits

• Automatic OCR adds a selection layer in the reader. The source PDF stays intact. Document-wide search, signature-label detection, and whole-document AI questions use the PDF’s embedded text.
• Ask AI uses extracted text, not page images, and includes up to about 400,000 characters of document text. Long documents may be truncated; AI answers can be wrong, so check the cited pages.
• Folio opens PDFs up to 300 MiB and 10,000 pages. Webpage conversion uses a separate session, so pages behind a login may not load. Desktop URL imports need a direct connection or an HTTP(S) system proxy that accepts numeric-address tunnels. Local-network access requires approval for the requested origin.
• On upgrading from 1.10.8 or earlier, Recent keeps the stored PDFs and rebuilds their previews when opened. Notes and chat on files up to 2 MiB keep their existing content identity. Larger files had only a partial hash, so Folio keeps those legacy records on disk without attaching them to a potentially different document.
• Automatic local saving is not cloud sync or a replacement for exporting a PDF copy. Password-protected documents are not saved in Folio between sessions.

Using Ask AI

Open Ask AI with the sparkle button in the toolbar, or select text and choose Ask AI in the pop-up toolbar. Then pick a provider at the top of the panel:

• ChatGPT: click Continue with ChatGPT and sign in in your browser. Questions use your ChatGPT plan (Go, Plus, or Pro), and usage counts toward that plan's limits; manage it in ChatGPT settings. Sign out, or change the default provider, in Folio's Settings.
• Claude: install Claude Code, run claude once in a terminal, and sign in with your Claude account (Pro or Max). Then click Check again in Folio. Questions use your Claude subscription.
• OpenRouter: under Settings → Ask AI, choose OpenRouter and verify your OpenRouter API key. Search the text models or enter a model ID. OpenRouter bills your key. Reopen this section to check the connection, replace the key, or remove it. If a model's context is too small for a document, choose a larger model or ask about a selected passage. For passage questions Folio sends the selected passage, page number, filename and conversation.

Ask AI is available in the desktop app only, not the browser version.

Privacy

Folio requires no Folio account, has no analytics or telemetry, and never uploads your documents on its own. It makes network requests only to:

• check GitHub for updates (installed copies; can be turned off in Settings),
• download the scan language packs you choose in Settings from the Tesseract.js project on GitHub,
• verify an OpenRouter key or retrieve model names during OpenRouter setup,
• open a link you give it (a webpage is loaded in a hidden, sandboxed window with its own temporary session, so no cookies or sign-ins are shared, and every permission is denied; its scripts run while it loads, as in any browser, and it's then printed to PDF), and
• answer a question you ask in Ask AI. Only then, the document's text (up to about 400,000 characters), any passage you selected, and the conversation go to the provider you chose: OpenAI for ChatGPT, or Anthropic through your installed Claude Code, or OpenRouter and the provider serving your chosen OpenRouter model. Their privacy terms apply to that data.

Folio stores an OpenRouter key only with operating-system credential protection. If secure storage is unavailable, enable or unlock your system key store to connect. For ChatGPT, Folio stores its sign-in tokens in its data folder (below, under ai), encrypted with the system's credential protection (Windows data protection, the macOS Keychain, or the Linux secret store; if a Linux desktop has no secret store, you sign in again each time Folio starts), and never exposes them to the page. For Claude, Folio runs your own Claude Code with every tool disabled; it never sees or stores your Claude credentials. The question's context is written to a temporary file for Claude Code and deleted as soon as the answer finishes. Each document's Ask AI conversation is saved with it on this computer (except for password-protected documents) and is there when you reopen the document; the + button in the panel starts over and deletes it.

Stored locally in your user profile (%APPDATA%\Folio on Windows, ~/Library/Application Support/Folio on macOS, ~/.config/Folio on Linux): recently opened PDFs and their thumbnails (up to 8, removable from the home screen with Clear all; password-protected PDFs are never kept), highlights, notes, and Ask AI conversations for each document (except password-protected ones), reading positions, preferences, and, only if you choose to remember it, your signature image. Apart from provider credentials, this data isn't encrypted, so anyone with access to your user account can read it.

Building from source

Requires Node.js 22 or newer.

npm install
npm run app        # build and run the desktop app
npm run smoke      # end-to-end check: launches the built app and exercises the basics
npm run dev        # browser version with hot reload at http://localhost:5173

npm run dist:win   # on Windows: release/Folio-Setup.exe and release/Folio-Portable.exe
npm run dist:mac   # on macOS: release/Folio-mac.dmg (universal: Apple Silicon and Intel)
npm run dist:linux # on Linux: release/Folio-linux-x86_64.AppImage and release/Folio-linux-amd64.deb

Each platform's installers are built on that platform; GitHub Actions builds all three for every release. If your terminal has ELECTRON_RUN_AS_NODE=1 set, unset it first.

How it's put together

• src/: the reader UI (React + TypeScript, built with Vite) on top of pdf.js. markup.ts saves and restores highlights and notes, NotesPanel.tsx and Selection.tsx are their UI, and AiPanel.tsx is the Ask AI panel.
• electron/: the desktop shell for Windows, macOS, and Linux. main.cjs serves the built app from dist/ over a custom app:// protocol with a strict Content Security Policy, runs the page sandboxed with context isolation, opens PDFs from the file manager, keeps a single window, downloads links, and handles updates. webpage.cjs converts webpages to PDF. ai.cjs runs Ask AI (ChatGPT sign-in and requests, OpenRouter keys and requests, and Claude Code). Stored credentials stay in the main process.
• scripts/release.mjs and .github/workflows/release-build.yml: the release pipeline (see CONTRIBUTING.md). scripts/smoke-test.mjs is the cross-platform smoke test CI runs. scripts/screenshots.mjs retakes the screenshots in this README (npm run build, then node scripts/screenshots.mjs).

Contributing

Bug reports and pull requests are welcome; see CONTRIBUTING.md. To report a security issue privately, see SECURITY.md.

License

MIT. Folio includes third-party software under its own licenses; see THIRD_PARTY_NOTICES.md.