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Merge PDF Files with macOS's Hidden join Tool

Concatenate several PDFs into one file using the Combine PDF Pages Automator action from the Terminal.

macOSFilesautomationpdfLow risk
Run "/System/Library/Automator/Combine PDF Pages.action/Contents/MacOS/join" -o merged.pdf a.pdf b.pdf to merge PDFs without third-party software.

01Command

Command
$ "/System/Library/Automator/Combine PDF Pages.action/Contents/MacOS/join" -o merged.pdf page1.pdf page2.pdf page3.pdf

02What it does

Every Mac ships with the Automator action 'Combine PDF Pages', and its command-line binary called join can be invoked directly from Terminal. Pass the output file with -o and list the input PDFs in the order you want them merged. Use shell wildcards like *.pdf to merge an entire folder of scanned pages at once.

03Risk

RiskLow risk
!Warning: On some macOS versions the binary lives at .../Combine PDF Pages.action/Contents/Resources/join.py and needs the full path quoted because of the spaces. Always quote paths containing spaces.

04Undo

✓No undo needed — this command does not change persistent state.

05Sources

  • Combine PDF files in Preview on Mac
    Apple · vendor-doc · 2026-09-17
    Evidence: Documents Apple's built-in PDF merging capability in Preview, which the Automator 'Combine PDF Pages' action uses under the hood.

Last verified: 2026-09-18 · Category: Media

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