The Complete Guide to Merging PDFs in Your Browser
Page-range syntax, queue ordering, what carries over, and the privacy model — everything you need to stitch PDFs together safely.
1. What merging a PDF actually means
Merging PDFs is the everyday task of stitching multiple documents — a signed contract, its exhibits, a scanned ID, an NDA — into one self-contained file you can email or file as a unit. Doing it in the browser means the documents never leave the device, which matters for any document covered by an NDA, HIPAA, or just basic confidentiality.
2. How page ranges work
Every file in the merge queue has a Page range box. Leave it blank to include the whole file. Type a comma-separated list of pages or ranges to include only those pages:
1-5, 8, 11-13— pages 1 through 5, page 8, and pages 11 through 133-— from page 3 to the end of that fileodd/even— only odd- or even-numbered pagesall— every page (same as leaving the box blank)
3. Why order matters and how to control it
PDFs merge top-to-bottom in the queue. Drag a row by its handle (the striped icon on the left) to reorder. Within each file, pages come out in the order written in your range — 5,1,3 would emit page 5 first, then 1, then 3 — so you can reorder pages within a file too.
4. What does not carry over
Page content, embedded fonts, images, and form-field widgets anchored to the copied pages all come through byte-identical. Document-level outlines (bookmarks) from the source PDFs are not carried across by copyPages — if you need a navigable outline on the merged file, rebuild it with the PDF Metadata Editor afterward.
5. Privacy & limits
The merge runs entirely client-side via pdf-lib. Nothing is uploaded; no server ever sees your files. There is no hard limit on the number of files, but because the browser holds every input PDF plus the merged output in memory, very large batches (~200 MB+) will slow down or hit the browser's memory ceiling. For huge jobs, merge in groups of 10–15 and then merge the result.
One File, Your Order, Zero Uploads
Merging is the most common PDF task and the cleanest one to do in the browser. Use page ranges to include only what you need, drag the queue into the order you want, and download a single self-contained file without your documents ever touching a server. For NDAs, contracts, and case files, that combination of precision and privacy is exactly right.