Two PDFs side by side,
scrolling together

A fast, fully native Windows viewer for reading two documents in parallel: a translation next to its original, two revisions of the same text, a paper and its appendix. The panes stay aligned even when the documents differ in length, page format and zoom.

Download installer Windows 64-bit · no admin rights needed Portable ZIP single .exe, nothing to install

Windows 10 or 11, x64. Free software under the GPLv3 · source code and all releases on GitHub

PDF Side Viewer with an Italian textbook on the left and its English edition on the right, both showing the same section 13.1 although the page numbers differ.
The same section in two editions of one book. Left: page 213 of 324. Right: page 222 of 329. Different pagination, different length, still in step, held here by 118 sync points.

Synchronized scrolling that survives real documents

Side-by-side viewers usually pair the two documents by pixel offset or by a fixed page difference. That falls apart as soon as the documents are not twins: a translation runs longer than its original, a revision adds a chapter, one file is A4 and the other is Letter.

Here positions are exchanged in page units, never in pixels, and the pairing is an anchor you set yourself: pre-scroll each pane to matching content, lock, done. Zoom each pane however you like, the alignment holds.

Adjust without losing the lock

Hold Alt and scroll to nudge one pane alone; the anchor is recaptured where you leave it.

Sync points, like WinMerge

Pin whole-page pairs ("page 5 left = page 4 right"). Between two points the panes move page for page.

Alignment gaps

Where one document has extra pages, the other shows an empty gap, so both panes keep scrolling one to one instead of drifting.

Points from bookmarks

Numbered outlines present in both files become sync points automatically, matching headings across fourteen languages.

Built for LaTeX work

Auto-reload: when a build rewrites a PDF on disk, the viewer reloads it in place and keeps position, zoom and sync. Recompile and just look up.

SyncTeX, both directions: Ctrl+click a spot in the PDF to open the matching source line in your editor (VS Code out of the box, any editor via a template), and a forward search from the editor scrolls the right pane to the target and flashes it. Each pane queries its own .synctex.gz, so a bilingual pair gets independent search on both sides.

A complete viewer in each pane

Reading

Continuous or page-by-page scrolling, fit width and fit page, tiled rendering that stays crisp to 800%, per-monitor DPI awareness.

Finding

Full-document text search with live highlighting, clickable links, an outline sidebar, go to page by number or by the document's own labels.

Text

Mouse selection, double-click for a word, Ctrl+C copies proper Unicode text.

Chrome that gets out of the way

Menu and toolbar share one row, movable Internet Explorer style, full screen, optional pane headers with the file name.

Picks up where you left off

Session restore, recent files and recent left-plus-right pairs, sync points remembered per document pair.

Fourteen languages

English, Italian, German, French, Hungarian, Ukrainian, Romanian, Portuguese, Greek, Spanish, Polish, Dutch, Czech, Swedish.

Native, and it shows

Pure Win32 and Direct2D, rendered by MuPDF, statically linked. No .NET, no Electron, no browser engine: one self-contained executable of about 25 MB that opens instantly. The portable ZIP needs no installation at all, and the installer runs per-user without administrator rights.

The optional Explorer entry ("Open left/right in PDF Side Viewer" on PDF files) is registered per user under SystemFileAssociations, so PDF Side Viewer can never take over as your default PDF handler.