Merge Multiple PDFs to Mac - how it works
The preview app can not just open PDF documents, annotate them, insert signatures, and even merge multiple PDFs into a single PDF. Here's how it works:
First, open the first PDF document in the preview app by double-clicking it. If PDFs on your Mac are linked to another application, right-click on the file and select "Open With"> "Preview". Click on "Presentation" in the upper left corner and then select "Miniature". In the sidebar you should now see all pages of the PDF. If not, Soe click on the little arrow next to filename so that it points down.
Now switch to the Finder and drag and drop the next PDF document into the preview app to the desired location in the sidebar. Make sure that the page number is displayed continuously, as it may happen that when you add a PDF at the end, it will still be individual documents.
The pages of the inserted file then flow smoothly into the pages the available over. You can also move individual pages to other locations using drag and drop. Once you're done, click the File drop-down menu in the menu bar and choose Save to overwrite the original PDF document. Alternatively, you can also select "Export as PDF" and give the merged PDF a new name.