How to compare two PDFs side by side on a Mac

Put two PDFs next to each other in Preview or your browser, keep them in step while you read, and what to use when you need the changes found for you.

Guide · Updated 13 October 2026

Open both PDFs in Preview. If they open as tabs in one window, drag one tab out to make it a window. Then tile them: Fn ⌃ ← for one and Fn ⌃ → for the other on macOS Sequoia and later.

Reading them together

  • In each window choose View, Single Page so pages line up.
  • Use ⌥ ⌘ 2 to show thumbnails, and jump both to the same page.
  • Zoom to fit the width (View, Zoom to Fit) so text is readable at half the screen.

When you need the differences found

Preview cannot highlight differences. Full PDF editors often have a compare tool, and a free option is to copy the text of each into a text compare tool. For contracts, the drafting app's own compare feature is more reliable.

Two PDFs and your notes

Comparing usually means notes too: three windows on a laptop screen. On a ClutterFreeMac strip, the two PDFs share the screen and your notes sit in the next column, one swipe away, never on top of a page you are reading. See researchers' window setup.

Questions

How do I open two PDFs side by side in Preview?

Make sure each is in its own window (drag a tab out if needed), then tile them with Fn ⌃ ← and Fn ⌃ → on macOS Sequoia and later.

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