Merging PDFs should not change how any page looks — and when done correctly, it does not. Each page in the combined PDF remains exactly as it was in the original file. The layout problems people experience when merging are almost always caused by the wrong tool, not by merging itself. Here is how to do it right.
The safest way to merge PDFs
A proper PDF merger combines files at the binary level — it reads the PDF structure of each file and joins them without re-rendering or re-compressing any page. This preserves fonts, images, colours, and layout with zero quality loss.
- Open Filero's free Merge PDF tool.
- Upload your PDF files — you can select multiple files at once.
- Drag to reorder the files in the sequence you want.
- Click Merge.
- Download your combined PDF — all pages preserved exactly.
Filero's merger runs entirely in your browser. Your files never leave your device, which is important for confidential documents like contracts, medical records, or financial statements.
Tools that damage layout when merging (and why)
Some tools — particularly online converters that convert PDFs to images, then merge the images, then convert back to PDF — destroy layout fidelity in the process. Signs that a tool has done this:
- Text becomes unselectable (it is now an image)
- File size increases dramatically
- Fonts look slightly different or blurry
- Colours shift slightly
A PDF-native merger (which Filero uses) never converts to images. If you notice any of the above symptoms after merging, switch to a different tool.
Merging PDFs with different page sizes
If you are merging PDFs of different page sizes — for example, a Letter-size document with an A4 document — the merged PDF will contain pages of different sizes. This is perfectly valid and all PDF readers handle it correctly. If you need all pages to be the same size, you will need to resize the pages before merging using a tool like Adobe Acrobat Pro, as there is no free browser tool that reliably handles page size normalisation.
How to merge PDFs in specific orders
Filero's Merge PDF tool lets you drag files into any order before combining. For common ordering scenarios:
- Cover page first: Upload the cover page PDF last, then drag it to the top position.
- Alphabetical order: Name your files alphabetically before uploading (File01, File02, etc.) — most operating systems will select them in alphabetical order.
- Insert in the middle: If you need to insert pages between existing pages, first split the original PDF using Filero's Split PDF tool, then merge in the order: Part 1 → new pages → Part 2.
Merging on iPhone and Android
The Merge PDF tool works fully in mobile browsers — no app download required. Open filero.app in Safari (iPhone) or Chrome (Android), tap the upload area, and select your files from Files (iPhone) or Downloads/Drive (Android). The merge runs in the browser and downloads the combined PDF to your device.
Frequently asked questions
Is there a limit on how many PDFs I can merge?
No. Filero's Merge PDF tool has no limit on the number of files. You can combine two or two hundred PDFs in one operation.
Will bookmarks and hyperlinks be preserved after merging?
Internal bookmarks (the PDF's table of contents entries) may not be preserved across files during a browser-based merge, as reconstructing the bookmark tree across multiple documents requires Acrobat-level processing. Hyperlinks to external URLs (web addresses) are preserved.
Can I merge password-protected PDFs?
You will need to unlock them first. Use Filero's Unlock PDF tool to remove the password (you need to know it), then merge the unlocked files.
Ready to try it?
Use Filero's free Merge PDF tool. No account needed, works on any device.
Open Merge PDF