How do I combine PDFs using the Preview app?

Insert full PDFs into another PDF

You can combine whole or parts of PDFs on a Mac using the Preview app.

Decide which PDF file you wish to be the primary document into which other documents or pages from documents will be inserted. Double clicking on this will open it in preview.

You can select "Duplicate" from the file menu to create a new file instead of overwriting your original primary document.

With the document open, make sure the thumbnails view is active by selecting View and making sure Thumbnails is checked. In the thumbnails, select the page after which you wish to insert content from another PDF.

Next, select Edit -> Insert -> Page from File

This will bring up a Finder window that allows you to select another PDF document. Select your secondary document and click on Open

The full secondary document will be inserted below the page selected in the thumbnails of the primary document

Don't forget to save your PDF when you are finished adding pages to it from other PDFs.

Inserting pages from one PDF into another PDF

Open the primary and the secondary document from which you will extract pages. Make sure thumbnails are showing by selecting View and making sure Thumbnails is checked.

It is helpful to have the files open side by side.

You can select "Duplicate" from the file menu to create a new file instead of overwriting your original primary document.

Press and hold the Command key ⌘, select the page thumbnails that you want to add to the other document, then release the key.

Drag the selected thumbnails from the secondary PDF into the sidebar of the primary PDF, then release where you want them to appear.

Once dragged over, the pages from your secondary document can be re-ordered, deleted, etc without affecting the source document from which they were copied.

Don't forget to save your PDF when you are finished adding pages to it from other PDFs.