Is my PDF uploaded to a server?
No. The file is read from your disk into the browser tab and processed there. After the page loads it makes no network requests.
Merge PDF files into one
Drop your PDFs, get a single combined file. The documents never leave your machine.
Drop PDF files here
or · max 10 files free
Merge PDFs without uploading them
Every other merge tool asks you to upload your documents to a server, waits while they transfer, then hands you a download link. For a one-page invoice that is merely annoying. For a signed contract, a medical record, or a client's financial statement it is a decision you cannot undo — that file now exists on someone else's disk.
PDFKit does the work inside the browser tab. The file bytes are read directly from your disk by the page, combined with a JavaScript PDF library, and written back out as a download. There is no server component at all: the site is static files on a CDN, so there is nothing that could receive your documents even if it wanted to.
What happens when you merge
Merging looks trivial and mostly is, but a few decisions actually matter on real files.
| Detail | Behaviour | What it means |
|---|---|---|
| Page order | Exactly as you dropped them | The merge follows the order you added files. If the sequence is wrong, start over with the correct order. |
| Page size | Each page keeps its own | A4 and Letter pages sit next to each other without being rescaled. |
| Annotations | Preserved | Form fields, highlights and comments travel with their page. Nothing is flattened. |
| Bookmarks | Dropped | The document outline is not carried across. The merged file has flat pages only. |
| Encrypted input | Cannot be read | If a PDF needs a password to open, the merge fails for that file. Remove the password first. |
| Output size | Sum of the inputs | Merging does not recompress. Nothing gets smaller, and nothing is re-encoded, so quality is identical. |
Five things people get wrong
Merging scanned batches without checking order
Scanners often produce files in reverse page order. Scroll to the bottom of the merged result before sending it anywhere.
Flattening forms by accident
Some tools flatten form fields during merge, turning fillable fields into pictures. This one does not, but check the output if a form stops being fillable.
Assuming merging compresses
A merged file is the sum of its parts. To reduce size, compress separately, before or after.
Trying to merge password-protected PDFs
The library cannot read an encrypted document. Decrypt it first.
Emailing a 200 MB merged scan
Gmail caps at 25 MB before encoding overhead. Compress or share a link instead.
Questions
How many PDFs can I merge at once?
10 files per batch on the free version. The offline version has no limit.
Does merging reduce quality?
No. Pages are copied as-is; nothing is re-rendered or recompressed.
Can I merge PDFs with different page sizes?
Yes. Each page keeps its original dimensions, so A4 and Letter documents can sit in the same file.
What happens to bookmarks and links?
Bookmark outlines are not carried over. Embedded hyperlinks inside pages are preserved.
Can I merge a PDF with a password?
No. Encrypted documents cannot be read. Decrypt them first.
Does it work offline?
Yes, once the page has loaded. Disconnect the network and the merge still runs.
Is there a file size limit?
No hard limit, but large files decode into memory. Hundreds of megabytes on a low-RAM machine can stall the tab.
Need it without a browser tab?
PDFKit Desktop is a single offline file — no 10-file limit, page-range selection, per-page rotation, adjustable watermark, and it never needs a network connection. One-time $19, no subscription.
See PDFKit Desktop — $19