everyday mac tools

Merge PDFs on a Mac without uploading them anywhere

· 6 min read

Open one of the PDFs in Preview, choose View, Thumbnails, then drag the other PDF from Finder into the sidebar. Preview inserts all of its pages, and Command-S saves the result. For a straight append with no reordering, select the files in Finder, right-click, and choose Quick Actions, Create PDF.

Both of those run entirely on your Mac. Nothing is uploaded, which matters more than it sounds when the documents are contracts, invoices, medical records or anything with a client’s name on it.

Merge in Preview, keeping the original intact

Preview is the tool for a merge where the page order matters and you want to see what you are doing.

  1. Open the first PDF in Preview. This is the document the others will be added to.
  2. Choose File, Duplicate, then save the copy under the name you want the merged document to have.
  3. Choose View, Thumbnails. The sidebar shows one thumbnail per page.
  4. Drag the second PDF from a Finder window into the sidebar. Watch for the horizontal insertion line between two thumbnails and drop it there, so the pages land where you expect rather than at the end.
  5. Repeat for each further file.
  6. Drag thumbnails up or down to fix the order. Command-click to pick up several pages that are not next to each other.
  7. Press Command-S.

Step two is the one people skip. Preview saves changes back into the document as you work, so pages you insert into the original are in the original until you undo them. Duplicating first turns the whole operation into something you can abandon by throwing the copy away.

If you prefer the menus to the mouse, Edit, Insert, Page from File does the same thing and inserts after whichever thumbnail is selected. On a long sidebar that is easier than aiming a drag.

The Finder Quick Action, for a straight append

When the files are already in the right order and you just want them in one document, you do not need to open anything.

  1. Put the PDFs in one folder.
  2. Switch the window to list view and sort by name, so the order is visible and predictable.
  3. Select them all.
  4. Right-click, then Quick Actions, Create PDF.

Finder writes a new PDF alongside the originals, named after the first file in the selection. None of the source files are changed. Images can go into the same selection: JPEGs, PNGs and HEICs each become a page, which is the quickest way to turn a set of photographed receipts into one document.

The limitation is order. The Quick Action follows the order the files appear in the window, not the order you clicked them, so if the sequence matters, rename the files with a numeric prefix (01-, 02-) before you start. There is no page-level control at all. If Create PDF is not in the menu, check System Settings, Privacy & Security, Extensions, where Finder extensions and Quick Actions are listed.

Straightening the pages while you are in there

A merge is usually the moment you notice that page 12 came out of the scanner sideways. Preview handles both while the sidebar is open.

  • Rotate: select the thumbnails and choose Tools, Rotate Left or Rotate Right. The rotation is saved into the file rather than being a viewing preference.
  • Delete: select a thumbnail and press Delete. Useful for the blank separator sheets scanners insert.

If what you actually want is the opposite operation, pulling a range out into its own file, Split a PDF into separate files on a Mac covers the sidebar and Shortcuts routes for that.

Merging forty files, or the same merge every month

Preview stops being reasonable somewhere around the tenth file. Automator is the built-in step up: its PDFs action library includes Combine PDF Pages, with a mode for appending pages end to end. Add it to a Quick Action that receives PDF files in Finder, follow it with Move Finder Items so the result lands somewhere you can find, and save it. It then appears in the same right-click menu as Create PDF. Automator will not sort the input for you, so file naming still does that job.

Past that, you are into dedicated PDF software. Basalt has a Merge tool alongside page tools for reordering and deleting, and a Procedures tool that records a set of steps so next month’s merge runs the same way as this month’s. It works on the Mac with no server involved, and every tool writes a new file rather than modifying the one you gave it. It is $29 for up to three Macs after a 24-hour trial. If your merging is two files, twice a year, Preview already does it.

What comes along with the merged file

A merged PDF is not only the pages you can see, which is worth knowing before you send one outside your organization.

The document metadata usually comes from the first file: title, author and creating application. Attachments embedded in any of the source documents can survive into the result. Bookmarks generally do not survive a Preview merge, so a document with a carefully built table of contents comes out flat.

Form fields are the sharp edge. PDF form fields are identified by name, so merging two filled copies of the same form can produce a document where both copies of a field share one value, because as far as the file is concerned they are the same field. If you are combining completed forms, flatten each one first, by printing it to PDF or by using your PDF software’s flatten command, so the answers become page content instead of live fields.

Once the merged file exists, it is a good moment to check what is in its properties before it goes out. Remove metadata from a PDF on a Mac before you share it covers that pass.

Merging does not hide anything

One thing merging definitely does not do is conceal content. Burying a page in the middle of a 200-page bundle leaves it fully searchable, fully selectable and fully extractable. Neither does putting a black shape over part of a page before you merge. If part of a document should not reach the recipient, remove those pages or redact them properly first, then merge.

Questions

Does merging reduce quality or make the file bigger than it should be? Page content is carried across as it is, with no re-encoding, so nothing degrades. The merged file is roughly the sum of the parts. If the total is unreasonable, the cause is almost always scanned images rather than the merge: Compress a PDF on a Mac without wrecking the scans covers what to do about that.

Can I merge a password-protected PDF? Only after it is open. Enter the password, and the methods above work normally. The merged file comes out without encryption unless you add a password to it again, which is easy to forget when the whole point was to keep the contents restricted.

Is there a Terminal command for this? Not any more. macOS used to ship a Python script inside the Automator action bundle that people called from the command line, and it went away with the system Python. An Automator Quick Action is the supported equivalent and can be triggered from Finder.

Why did my merged PDF lose its links? Internal links and bookmarks depend on document structure that a page-level merge does not rebuild. External web links inside page content usually survive; links pointing to a page number in the old document generally do not, because that page number now means something else.