How to Combine PDFs on Mac — Preview Method, Online Tool, and Automator Batch

Mac has a built-in PDF merger — Preview. No Adobe, no download, no cost. Here is how to use it, plus faster methods for large batches.

Method 1: Preview (Built-In, Free)

1. Open the first PDF in Preview (double-click usually opens in Preview)
2. Click View → Thumbnails to show the sidebar
3. Open Finder next to Preview so you can see your other PDF files
4. Drag the second PDF from Finder into the sidebar — drop it where you want it (above or below existing pages)
5. Repeat for additional PDFs
6. File → Export as PDF → choose save location → Save

Critical: Use "Export as PDF" not "Save." "Save" overwrites your original first file. "Export" creates a new merged file.

Mac Merge Methods Compared

Method	Speed	Batch Support	Reorder Pages?	Best For
Preview	Quick for 2-3 files	✗ One at a time drag	✓ Yes — drag thumbnails	Most Mac users, small merges
Online tool	Quick for any count	✓ Upload all at once	✓ Yes — drag to reorder	Large merges, non-Mac sharing
Automator Quick Action	Instant after setup	✓ Select all → right-click	✗ Alphabetical order	Repeated batch merges
Terminal (pdfunite)	Instant	✓ Command line glob	✗ File name order	Developers, scripting

Method 2: Online Merger (Any Device)

When Preview is not enough — merging 10+ files, need precise reordering, or sharing the workflow with non-Mac colleagues:

1. Open PDF merger in Safari
2. Drag all your PDFs at once — upload multiple files
3. Reorder by dragging
4. Click Merge → download the result

Method 3: Automator (Batch Processing)

For repeated merging tasks (weekly reports, monthly invoices):

1. Open Automator (search in Spotlight)
2. Choose Quick Action
3. Set "Workflow receives current" to PDF files in Finder
4. Drag "Combine PDF Pages" from the library into the workflow
5. Add "Move Finder Items" to set the output location
6. File → Save — name it "Merge PDFs"
7. Now select any PDFs in Finder → right-click → Quick Actions → Merge PDFs

Troubleshooting Mac PDF Merge

• "I accidentally saved over my original" — if you used "Save" instead of "Export," your original first file now contains all merged pages. Use Cmd+Z (Undo) immediately if still in Preview. If Preview is closed, check Time Machine backups
• "Pages are in the wrong order" — in Preview's sidebar, drag thumbnails to reorder before exporting
• "Some pages are different sizes" — this is normal. Each page keeps its original dimensions. Mixed Letter/A4 is common when combining documents from different sources
• "Preview won't let me drag a PDF into the sidebar" — make sure the Thumbnails sidebar is visible (View → Thumbnails). Drag the file onto a thumbnail, not into empty space