Why Merge PDF Files?
Combining multiple PDFs into a single document is one of the most common file operations. Whether you're assembling a report from separate chapters, consolidating invoices for accounting, or packaging application materials, merging saves time and keeps documents organized.
The key concern is how and where the merge happens. Most online services upload your files to their servers. Local tools process everything on your device, so the file contents never leave it.
Local Merge vs Cloud Services Compared
| Feature | Local Merge (Allin PDF) | Typical Cloud Services |
|---|---|---|
| File Upload | No — processed in browser | Yes — uploaded to remote server |
| Privacy | Files never leave your device | Files pass through the provider's servers |
| Speed | No upload or download wait | Depends on upload speed and queue |
| File Reordering | Drag-and-drop on desktop | Varies by service |
| Bookmark Preservation | No — bookmarks are not carried over | Varies by service |
| File Size Limit | 5MB per file free, 50MB per file Pro | Varies by plan |
| Internet Connection | Needed to open the web app; for fully offline use, use the iOS app | Required |
Step-by-Step: How to Merge PDFs with Allin PDF
- Open the merge tool — Go to app.allinpdfapp.com/tools/merge-pdf. No account needed.
- Add your files — Drag and drop 2–20 PDF files into the drop area, or click to browse.
- Reorder files — The file at the top of the list comes first. On desktop, drag rows into your preferred order. Mobile browsers may not support dragging, so select the files in the order you want.
- Click Merge — Processing happens locally in your browser.
- Download the result — Your merged PDF is saved as
first-file-name_merged.pdf. Your original files are unchanged.
Merging PDFs on Windows, Mac and iPhone
Windows
Windows 10 and 11 have no built-in way to merge PDFs. Edge and the Photos app can display a PDF but cannot combine files. The easiest option is a browser-based merge tool in Chrome or Edge, which needs no installation and works on locked-down work computers.
Mac
On a Mac you can merge PDFs with the built-in Preview app:
- Open the first PDF in Preview.
- Choose View → Thumbnails to show the sidebar.
- Drag the other PDFs from Finder into the sidebar and drop them where you want them.
- Choose File → Export as PDF… to save the combined file.
iPhone and iPad
On iPhone, the Files app can combine PDFs:
- Open the folder with your PDFs in the Files app.
- Tap the More button (…) at the top right, then Select, and pick the PDFs.
- Tap the More button (…) at the bottom right and choose Create PDF.
For more control over the order, you can also use the Allin PDF iPhone app.
What Merging Keeps and What It Doesn't
- Kept: page content, text and image quality, and page size (A4, Letter, etc.), because pages are copied without re-encoding.
- Not kept: bookmarks (outlines) from the source files are not carried over to the merged PDF. If you need a table of contents in the sidebar, add bookmarks again in a PDF editor after merging.
- Password-protected files: PDFs that need a password to open must be unlocked first with Unlock PDF. You can protect the merged file again with Encrypt PDF.
- Only some pages needed: extract them first with Split PDF, then merge.
FAQ
Is there a limit to how many PDFs I can merge at once?
With Allin PDF, you can merge up to 20 files at once. Each file can be up to 5MB on the free plan and up to 50MB on Pro. For more than 20 files, merge them in batches and then merge the results.
Will merging PDFs reduce the quality of my documents?
No. PDF merging is a lossless operation — it combines the internal structures without re-encoding images or text. The output quality is identical to the source files. Only compression tools alter quality.
Are bookmarks preserved?
No. Allin PDF does not carry bookmarks from the source files over to the merged PDF. The page content itself stays exactly the same.
Can I merge password-protected PDFs?
Not directly. Remove the open password first with Unlock PDF (you need to know the current password), then merge the files as usual. The merged output can then be re-protected with Encrypt PDF if needed.