PDF Merger
Merge multiple PDFs into one, drag to reorder, choose page ranges per document — 100% in your browser.
PDF Merger
1-3,5,7-9 to grab only those pages from that document. Order in the merged PDF matches the order shown above — drag rows to rearrange.
How to merge PDFs
Add your PDFs
Drag and drop your PDF files onto the dropzone, or click to pick them. Each file gets a row showing its name, page count, and size. You can add as many as you like — there's no upload limit because nothing is uploaded.
Reorder if needed
The merge order matches list order from top to bottom. Use the up/down arrows next to each row, or drag the row by the ⋮⋮ handle to rearrange. The first PDF in the list becomes pages 1+ of the output.
Pick page ranges (optional)
Leave the range field blank to include every page. Or type a range like 1-3,5,7-9 to grab only those pages from that document. Useful for combining a cover letter (page 1 only) with a full resume (pages 1-3) into one PDF.
Click Merge and download
The merged PDF is built in your browser and saved as merged.pdf. Larger merges (50+ pages, many images) may take a few seconds — pdf-lib is fast but not instant. The download is the complete result; no second step needed.
PDF merging — surprisingly complicated, finally easy
PDF was designed so a document looks the same on any computer, which means the file carries what it needs to render — fonts, images, layout instructions and, later, form fields. It is also why merging PDFs is harder than concatenating two text files: every page is a web of objects it points to, and the merged file must copy each page with everything it references, then write a new cross-reference table that says where every object sits. Since 2008 the format has been an open international standard, ISO 32000-1:2008.
Why most "free online PDF tools" are not free
Open a tab. Search for "merge PDF online". You'll get dozens of sites that ask you to upload your files, watch a progress bar, wait, then download the merged result. The dirty secret of that workflow: your PDFs were just uploaded to a stranger's server. Many of these sites are legitimate and delete files after a few hours. Some are not. Any of them can see what you uploaded, when, and from which IP address. If your PDF is a tax return, an employment contract, a medical record, or anything containing names and account numbers — uploading it to an unknown server crosses a privacy line that you probably wouldn't cross knowingly.
The merge happens in your browser tab with pdf-lib, an open-source MIT-licensed library served from this site — your files are never uploaded.
What "100% client-side" actually means
The pdf-lib library — open-source, MIT-licensed, 525 KB minified (about 206 KB gzipped) — runs entirely in your browser tab. When you drop a PDF, it's read into an ArrayBuffer in memory (never on disk, never on a server). When you click Merge, pdf-lib walks through each source PDF's object table, copies the pages you want into a new in-memory document, and writes that back out as a Blob your browser can save. Because the output is a new document, document-level parts of the sources — bookmarks, the title and author, and the form (fields keep showing their values but stop being fillable) — are not carried over. You can verify this yourself: open DevTools, switch to the Network tab, drop your PDFs, click Merge, watch — there is no outbound traffic. The page only loaded the pdf-lib script itself (cached after first visit) and the page CSS. Your PDFs go nowhere.
What a page range does
Each document in the list can take a page range — 1-3,5 for pages 1 to 3 and 5, blank for every page. The same file can be added twice with different ranges, which is how you move one page elsewhere in the merged file. A range that names a page the file does not have stops the merge with the file's name and the problem, instead of silently leaving pages out.
What you can't do (yet)
This tool merges PDFs in the order you arrange them, with optional per-document page selection. What it doesn't do (yet): split a single PDF into pieces, rotate pages, add page numbers, add bookmarks, OCR scanned text into selectable form, or strip passwords from encrypted PDFs. Most of those are on the roadmap. For now, if your PDF is password-protected, you need to remove the password in Adobe Acrobat or Preview (macOS) first — the tool cannot open a file it cannot decrypt. And for visual editing of PDF content (text changes, image swaps), no in-browser tool is yet good enough to recommend — that's still desktop software territory.
ISO 32000, a ten-digit offset, and what a merge leaves behind
A merge copies pages, not documents: bookmarks, the title and the form of each source stay behind, because they live at document level.
PDF has been an open international standard since 2008 — ISO 32000-1, PDF 1.7.
A classic cross-reference table gives byte offsets ten digits, capping a file at 1010 bytes (about 10 GB); cross-reference streams lift the limit (ISO 32000-1, Annex C).
PDF/A is a separate ISO standard (ISO 19005) for long-term archiving — a merge here does not keep a file PDF/A-conformant.
A single PDF file can contain JavaScript, multimedia, 3D models, form fields, digital signatures, and even other PDFs embedded as attachments.
Page ranges are checked before anything is built: 12-15 on a 10-page file stops the merge rather than dropping those pages.
PDF/X (X for "exchange") is a printing-industry variant that requires all fonts and images to be embedded — used for sending print-ready files to commercial printers.
PDF encryption has used RC4 and, since PDF 1.6, AES (the AESV2 crypt filter); how strong a protected file is still depends on its password.
Tagged PDF, marked by the MarkInfo dictionary added in PDF 1.4, gives screen readers a document structure to navigate.
pdf-lib, the MIT-licensed library behind this tool, is 525 KB minified — about 206 KB gzipped — and is served from this site.
FAQ
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No. The pdf-lib library runs entirely in your browser tab. PDFs are read into memory, merged in memory, and saved back to your downloads. Nothing is sent to RECATOOLS servers. You can verify by opening DevTools → Network and watching for outbound traffic when you click Merge — there is none.
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Soft limit only — your browser's memory. If your browser tab crashes during merge, the combined files were too big — split into batches and merge the results.
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No — not even one that opens without a password. "Restriction-only" protection (an owner password that blocks printing or editing) still encrypts the file's text and images, and pdf-lib, the library this tool uses, cannot decrypt them, so anything it saved would be broken. Since 30 September 2026 the tool says so as soon as you add such a file, instead of merging in pages that would not open. Save an unprotected copy first, in software that has the password.
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Type page numbers separated by commas, or ranges with hyphens. Examples:
1(page 1 only),1-5(pages 1 through 5),1,3,5(pages 1, 3, 5),1-3,8,10-12(mix). Blank field = all pages. -
Yes — add the same PDF twice, set page-range
3on the first instance and1-2,4-10on the second. The merge will give you pages 3, 1, 2, 4, 5... etc. Clunky but works. -
Internal hyperlinks within each source PDF are preserved. Bookmarks (the table-of-contents sidebar in Acrobat) are not preserved in this version. Form fields are flattened. For preserving bookmarks, use a desktop tool like PDFsam.
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Not directly. Convert Word/Excel to PDF first (use Print → Save as PDF in any office app). For images, use our Screenshot to PDF tool to convert JPG/PNG into PDF, then merge here.
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Usually means the PDF is corrupted (try opening it in a viewer first), password-protected (remove the password), or uses a structure pdf-lib cannot read. Try re-saving it from Adobe Acrobat or your PDF viewer, then try again.
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Producer and Creator are set to "RECATOOLS PDF Merger". Creation date is now. The merged document does NOT inherit metadata from the source PDFs — useful if you want to scrub source-file metadata. Author and Title remain blank unless you edit the result in Acrobat.
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Yes on iOS Safari and Chrome on Android. Use the "Choose files" button (drag-and-drop is desktop-only on most phones). Larger merges may run out of memory on older phones — merge in smaller batches if the tab reloads.
Method & sources
How it computes
Copies the chosen pages of each PDF, in list order, into a new document with pdf-lib. Page ranges ("1-3,5") are checked before anything is built: a part that is not a page number, or names a page the file does not have, stops the merge with the file's name.
What this tool implements
- Until this review a mistyped range was silently skipped — "12-15" on a 10-page file dropped those pages, or the whole document, and an all-invalid set downloaded an empty PDF.
- ISO 32000-1 Annex C: a classic cross-reference table's ten-digit offsets limit a file to 10^10 bytes (about 10 GB), a limit cross-reference streams lift — the page had said 10 terabytes. It also claimed a 67-byte minimum file and pdf-lib doing "95% of Acrobat", and was removed.
- Because the output is a new document, bookmarks, title/author and the form's fillability are not carried over; the page now says so.
Sources
- ISO. ISO 32000-1:2008, Portable document format — Part 1: PDF 1.7 (Annex C, Architectural limits). https://www.iso.org/standard/51502.html
- Adobe. PDF 32000-1:2008 (free copy of ISO 32000-1). https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF…
- Hopding A. PDF-LIB. https://pdf-lib.js.org/
Pick up where you left off
Stored only in this browser — never sent to our servers.