Merge PDF files
Combine any number of PDFs into one document in the order you choose, without uploading a single page.
Drag files here, or
Your documents are read in this tab. They are never uploaded.
Ready · runs on your device
Nothing is uploaded. This tool runs entirely inside your browser tab. Your files and figures stay on your device - we never receive them, so we cannot read, store or lose them.
What merging actually does
Merging is not stitching files end to end. Each source document is parsed into its object graph - pages, fonts, images, colour spaces - and the pages you want are copied into a new document along with every resource they depend on.
That copying is why fonts do not break and images do not shift. A merge that simply concatenated bytes would produce an unreadable file, because a PDF’s cross-reference table indexes byte offsets that concatenation would invalidate.
Ordering
Files merge in the order shown, and the arrows let you rearrange before you commit. Two habits save time:
Name files so they sort correctly. Prefix with zero-padded numbers - 01-cover.pdf, 02-report.pdf - so the order is already right when you select them.
Check the page counts. The list shows how many pages each file contributes. A file with an unexpected count is usually a sign you picked up the wrong version.
Where this gets used
- Contracts and signature pages. Assembling a signed agreement from separately signed parts - precisely the case where uploading to a third party is least appropriate.
- Applications. Combining a CV, cover letter, transcripts and certificates into the single PDF a portal demands.
- Invoicing and expenses. Merging receipts into one submission.
- Reports. Joining a cover page, body and appendices exported from different tools.
- Scanned documents. Combining pages scanned in separate batches, or a double-sided scan captured as two files.
What is preserved and what is not
Preserved: page content, vector graphics, embedded fonts, images, page dimensions and rotation, and any annotations attached to a page.
Not preserved: the bookmark outline, interactive form field definitions, document-level JavaScript, attachments and digital signatures.
That last one is worth stating clearly: merging invalidates a digital signature. A signature certifies a specific byte sequence, and merging necessarily produces a new one. If a document must remain verifiably signed, it cannot be merged - sign the combined document instead.
Mixed page sizes
Pages keep their original dimensions. Merging A4 and US Letter documents produces a PDF with both sizes in it, which is valid and displays correctly but may print inconsistently. Most PDF readers offer “fit to page” at print time, which resolves it.
Reducing the result
Merged documents inherit everything from their sources, including duplicate embedded font subsets. Running the result through the PDF compressor in lossless mode consolidates the object structure and typically reclaims some of that overhead without touching quality.
Common questions
How is this different from iLovePDF or Smallpdf?
Those services upload your document to their servers, merge it there and send it back. Their privacy policies describe how long copies are retained - typically an hour or a few hours. This tool never transmits anything at all - pdf-lib parses and rebuilds the document inside your browser tab. For contracts, medical records, financial statements or anything under NDA, that difference is the whole point.
Is there a file size or page limit?
No imposed limit, only your device's memory. Documents totalling a few hundred megabytes generally work on a desktop; phones have considerably less headroom. If the tab becomes unresponsive, merge in smaller groups.
Are bookmarks and form fields preserved?
Page content, embedded fonts and images are copied faithfully. Document-level structures - the bookmark outline, form field definitions and JavaScript actions - are not carried across, because they belong to the source document rather than to individual pages. Merged forms will retain their visual appearance but lose interactivity.
What about password-protected PDFs?
Files with an owner password that still permit reading will usually open. Files requiring a password to open at all cannot be processed - remove the password in your PDF reader first, which requires you to know it.
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