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How to merge PDFs on a Mac: Finder, Preview and Terminal

Combine PDFs on a Mac with Finder, Preview's sidebar or one Terminal command, and what to do when the merged pages come out in different sizes.

Your Mac can already merge PDFs three different ways. All of them work on your Mac, and none needs an account.

1. Finder

  1. Select the PDFs in Finder, in the order you want them.
  2. Control click the selection.
  3. Choose Quick Actions > Create PDF.

2. Preview

  1. Open the first PDF in Preview and choose View > Thumbnails.
  2. Drag the other PDFs from Finder into the sidebar, where you want them to go.
  3. Drag thumbnails to reorder, then File > Export as PDF to save a new file.

3. Terminal

macOS ships a small merging tool inside Automator. Checked on macOS 26.6.2 on 1 October 2026:

"/System/Library/Automator/Combine PDF Pages.action/Contents/MacOS/join" \
  -o merged.pdf first.pdf second.pdf

When the pages come out different sizes

All three keep each page at its original size, so a letter sized page next to an A4 scan looks wrong on screen and prints unevenly. Preview has no setting to make them match. Simply PDF can bring every page to one size as it merges, and keeps bookmarks and links from the originals.

Questions

How do I combine PDFs on a Mac for free?

Select the files in Finder, Control click, and choose Quick Actions > Create PDF. Preview's thumbnail sidebar and the built in join command in Terminal work too.

Why are the pages different sizes after merging?

Merging keeps every page at its original size. Pages from different sources, such as letter and A4, stay mismatched unless a tool resizes them to one size.

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