PDF document tool
Merge PDF
Join PDF documents into one file in the order you choose, in this browser tab.
Formats, sizes, and limits
- Accepted formats
- Maximum documents
- Up to 10 PDFs per merge
- File size limit
- 30 MB per file · 100 MB total
- Combined pages
- Up to 200 pages
- Output
- Standard PDF document
- Choose PDFs
- Arrange order
- Merge & download
Step 1
Choose PDF documents to combine
Select up to 10 PDF documents.
Drop your PDF documents here
or
PDF only. Up to 10 documents · Max 30 MB each · 100 MB total · 200 pages combined.
Processed entirely in this tab. Your files never leave your device.
Step 2
Document order
Documents merge top to bottom in this exact order. Pages inside each document keep their original sequence.
Step 3
Merge documents
Your source files stay unchanged. The merged document is created fresh in this tab.
Before you merge
- Digital signatures: any digital signatures in the source documents will not remain valid in the merged file.
- Advanced features: bookmarks, attachments, annotations, layers, tags, and similar structures may not be preserved. Documents with interactive form fields are rejected in this milestone because forms cannot be merged reliably yet.
- Originals untouched: your source files are never modified — only a new merged file is created.
- Not a sanitizer: this tool does not strip scripts or other active content from PDFs. Review untrusted documents before opening the result.
Add at least 2 valid PDF documents to merge.
Source preview
Selected documents
First page of each document you added — this is a preview of your inputs, not of the merged result.
Input preview · shows the first page of each selected document
Merged PDF document
Your merged document is ready. Review it below or download.
- Documents
- 0 documents
- Pages
- 0 pages
- File size
- 0 KB
merged.pdf
Merged PDF preview
Saved as a standard PDF. Viewable in any PDF reader or browser.
Document standards
Merging you can verify
Combining documents while keeping page fidelity, honest limitations, and your originals intact.
Order you control
Documents merge in the exact top-to-bottom order shown in the queue, and the pages inside each document keep their original sequence. Rearrange with the Move up and Move down buttons at any time.
Verified before download
After merging, FileMizo re-opens the finished file and checks that it parses as a PDF, that the page count matches the sources, and that every page's dimensions and rotation survived intact.
Private by design
Every step — parsing, page copying, and assembly — runs inside your browser tab with pdf-lib. Your documents never leave your device, and your original files are never modified.
Step-by-step
How to merge PDF documents
- 1. Select your PDFs: Drag and drop up to 10 PDF files or choose them from your device. Each file is parsed and validated before it enters the queue.
- 2. Order your documents: Use the Move up and Move down buttons to set the sequence. The first document's pages become the opening pages of the result.
- 3. Review the disclosures: Check the signature, advanced-feature, and sanitizer notes above the Merge button, and set your output filename.
- 4. Merge: Click Merge PDF documents and watch live progress. Cancel anytime — changing the queue also discards stale results.
- 5. Preview and download: Page through the verified merged document in the result preview and download your .pdf file.
Frequently asked questions
Merge PDF answers
How do I combine several PDFs into one document?
Drop or select up to 10 PDF files into the upload area. Arrange them in the order you want, check the output filename, and click 'Merge PDF documents'. The finished file can be previewed page by page and downloaded instantly.
In what order are the documents and pages merged?
Documents are joined in the exact order shown in the Document order list — the first document's pages become the first pages of the result, then the second document follows, and so on. Within each document, pages keep their original sequence. This tool does not extract, split, or reorder individual pages.
Will digital signatures in my PDFs still be valid after merging?
No. Digital signatures cover the exact bytes of a document, so copying pages into a new merged file invalidates them. If you need a signed document to stay signed, do not merge it — keep the original file instead.
Can I merge password-protected or locked PDFs?
No. Password-protected documents are rejected with a clear message because their pages cannot be read without the password. Remove the password with your PDF reader first, then add the document again.
What happens to form fields, bookmarks, and annotations?
Documents with interactive form fields are rejected in this milestone because forms cannot be merged reliably yet. Bookmarks, attachments, annotations, layers, tags, and similar advanced structures may not be preserved in the merged output — review the result before relying on them. These limitations are stated above the Merge button as well.
Does merging compress or sanitize my PDFs?
No. Merging only combines documents — it is not compression (if the result is larger than the sources, the tool says so) and it does not strip scripts or other active content from PDFs. Review untrusted documents before opening the merged file.
Are my files uploaded to any server or processed remotely?
No. Every step — parsing, page copying, verification, and previews — happens inside this browser tab. No file bytes or filenames are ever sent to any server, and your source files stay unchanged.
Can I cancel a merge that is already running?
Yes. A Cancel button appears while the merge is in progress. Cancelling discards any partial work, and changing the document order or queue after a merge also clears the previous result so you can never download a stale file.