Combining PDF files without Adobe is straightforward — Preview on Mac has done it for years, and browser-based tools handle it on any platform. Neither requires a subscription or installation.
On Mac: Use Preview
Open the first PDF in Preview and show the thumbnail panel: View → Thumbnails. Then drag the second PDF file from Finder directly into Preview's thumbnail panel, dropping it at the position where you want it to appear. Preview inserts its pages at that point. Repeat for additional files, reorder pages by dragging thumbnails if needed, then go to File → Export as PDF to save the combined document.
Alternatively, select multiple PDFs in Finder at once, right-click, and choose Open With → Preview. All files open together as a single document in page order. This is faster when you just want to append files in the order they're sorted.
On Any Platform: Browser-Based Tool
WukongPDF's Merge PDF tool works in any browser without installation. Upload the files, drag to reorder them if needed, and download the combined PDF. It handles Windows, Mac, Chromebook, and mobile equally well — useful when you're not on your own machine or need to merge more than a few files at once.
For large batches, naming your files with leading numbers before uploading (01_intro.pdf, 02_main.pdf, 03_appendix.pdf) means they'll already be in the right order when the tool lists them, saving the drag-reorder step.
On Windows Without Word or a Browser Tool
Windows doesn't have a built-in PDF merger equivalent to Preview. If you have Microsoft Word installed, you can insert one PDF into another as an object, but this embeds it as an image rather than merging the pages properly — not what you want. The browser tool is the simplest free path on Windows.
File Size After Merging
The merged PDF will be approximately the combined size of the source files. If the result is larger than you need for email or upload purposes, running it through a compression tool afterward brings it down without affecting the content. Merge first, compress after — compressing before merging works too, but doing it once at the end is simpler.