Mac has a completely free built-in method for merging PDFs that most people don't know about — it's been in Preview for years. No downloads, no subscriptions, no websites. If you've been looking for a free way to combine PDFs on Mac, you already have it.
The Preview Method: Completely Free and Built-In
Here's the exact workflow. Open the first PDF in Preview. Show the thumbnail sidebar by going to View → Thumbnails (or pressing Option+Cmd+2). Now open the second PDF in a separate Finder window. Drag the second PDF file from Finder directly into Preview's thumbnail panel, dropping it where you want it to appear in the document — after the last page to append it, or between existing pages to insert it.
Preview inserts the pages from the dragged PDF into the open document. Repeat for additional PDFs. When you have all the pages in the right order, go to File → Export as PDF and save the combined document. The original files are unchanged.
Controlling Page Order
Once pages are in the thumbnail panel, you can drag them to reorder. Click a page thumbnail and drag it up or down in the panel to move it. To select multiple pages at once, hold Cmd and click each thumbnail. This lets you reorder pages from the merged documents, delete unwanted pages, or rearrange everything before saving.
One thing to watch: if you accidentally drag pages out of order, undo works normally (Cmd+Z). If the thumbnail panel closes and you lose your progress, the undo history persists — keep undoing until you get back to where you were.
Alternative: Drag Multiple Files at Once in Finder
For a faster way to open multiple PDFs in Preview together: select all the PDF files in Finder (click one, then Cmd+click the others), right-click → Open With → Preview. All selected files open as a single document in Preview with each file's pages in sequence. The order follows the selection order in Finder, which is usually alphabetical or chronological depending on your sorting.
Then use File → Export as PDF to save the combined document. This is the quickest path when you want to merge all the PDFs in a folder in their current sorted order.
When to Use a Browser Tool Instead
Preview works well for merging a handful of PDFs. For larger numbers of files — 10 or more — or for situations where you need to merge specific pages from different documents rather than entire files, a browser-based Merge PDF tool is more efficient. Upload the files, arrange them in the interface, and download the result. Browser tools also typically give you a visual preview of the final page order before you commit.
WukongPDF's merge tool accepts multiple files and lets you drag to reorder before merging — a cleaner interface than Preview's thumbnail panel for complex multi-file merges. Both methods are free; Preview is better for quick two- or three-file merges, the browser tool for more complex combinations.