How this works in your browser
Merging is done with pdf-lib running inside your browser tab. A PDF is essentially a collection of page objects plus the fonts, images and resources they reference, so combining files does not require rendering anything: pdf-lib copies each source page object, along with the resources it depends on, into a single new document and writes out one file. Because no page is ever rasterised or re-encoded, text stays selectable, fonts stay embedded and image resolution is untouched. It is also why merging is fast even for large documents, and why nothing needs to be uploaded to a server to do it.
Merge PDF vs. traditional online converters
| Feature | Merge PDF (in-browser) | Traditional online converters |
|---|---|---|
| File upload required | No - never leaves your device | Yes - file is sent to a server |
| Processing queue | None - starts instantly | Often, especially at peak times |
| Watermark on output | Never | Common on free plans |
| Usage limits | None - free, unlimited use | Often capped per day or file size |
| Works offline once loaded | Yes, for most tools | No - requires a live connection |
| Account required | No | Often, for anything beyond a trial |
How to use Merge PDF
- 1
Open the Merge PDF tool
Go to tools.slaytic.com and open the Merge PDF tool. No sign-up or account required.
- 2
Drop your PDFs and order them
Drop in as many files as you need, then drag them into the exact order you want. Remove any file from the list before merging if you change your mind.
- 3
Merge and download
Click Merge and the combined document is assembled in your browser and offered for download immediately.
Common ways to use Merge PDF
Assembling a report or submission
Combine a cover letter, main document and appendices into one file that reads in the right order for the recipient.
Joining scanned pages
Turn a folder of individually scanned pages into a single document instead of sending a dozen separate attachments.
Packaging client deliverables
Merge invoices, contracts and supporting documents into one clean PDF without those files passing through a third party.
Frequently asked questions
How many PDFs can I merge at once?
There is no hard limit on the number of files. Very large batches (hundreds of pages) may slow down on older devices since all processing happens in your browser, but for typical use there is no restriction.
Will the quality of my PDFs be affected?
No. pdf-lib stitches pages together directly without re-rendering any content, so text sharpness, image resolution, and embedded fonts are all preserved exactly as in the originals.
Can I reorder the files before merging?
Yes - after dropping your files you can drag them into any order before clicking Merge. You can also remove individual files from the list if you change your mind.
Are bookmarks, links and form fields preserved?
Page content, text and images carry over exactly. Document-level features like outlines, internal link targets and form fields are less reliable across a merge, since they reference page positions that shift when documents are combined. Check the output if your source PDFs rely on them.
What happens if the PDFs are different page sizes?
Nothing breaks. Each page keeps its own dimensions, so an A4 report merged with a US Letter scan produces a document where those pages differ in size, exactly as they did originally.
Can I merge a password-protected PDF?
Not while it is still encrypted. Remove the password first with the Unlock PDF tool, then merge the unlocked copy.