How to Merge PDFs in the Right Order, with a Worked Example
Merge PDF appends whole documents in the order shown in its file list. For example, a two-page cover document followed by a one-page attachment becomes a three-page PDF. It does not number the pages, resize them to a common paper size or remove duplicate content.
Combine files and check their order
- Open Merge PDF and choose or drop at least two PDF files.
- Check the filenames in the list. Use ▲ and ▼ to move each file up or down; use ✕ to remove an accidental selection.
- Put the document that should be read first at the top. All of its pages will appear before any page from the next file.
- Select Merge PDFs. The result downloads as
merged.pdf. - Open that download and check the total page count, the first and last pages, and the boundary between each source document.
Keep the source documents so that you can rebuild the result if an attachment is missing. The tool creates a new file; choosing files does not overwrite them.
A three-page example you can reproduce
Download sample-a.pdf, which has two labelled pages, and sample-b.pdf, which has one. Add A first and B second, then merge.
The expected result is A1 → A2 → B1, three pages in total. The samples use different page sizes, so the output should retain those differences. Compare it with the saved merged result. Reverse the file order and the expected sequence becomes B1 → A1 → A2.
The first sequence and original page sizes are recorded in our September 13, 2026 processing checks. Those checks cover these sample files and the merging function, not every PDF feature or browser.
Match the tool to the document
- Only part of an attachment belongs in the result: use Split PDF to extract those pages first.
- One page needs to move between documents: merge, then use Organize PDF for page-level ordering.
- The result exceeds an upload limit: check its actual size, then consider Compress PDF. Compression uses server processing and can change image quality.
- The documents contain fillable fields or existing digital signatures: inspect those features separately in a PDF reader. A correct page count does not establish that forms, bookmarks or signature validation survived the merge.
If merging fails
Try the public samples first. If they work but your files do not, open each source in a PDF reader and check for password prompts, damaged pages or an incomplete download. This merge interface does not provide a password field. Obtain an accessible copy from the document owner when necessary.
A large collection of scanned pages can exhaust browser memory. Close other heavy tabs, try smaller batches, and inspect each intermediate result before merging the batches.
This tool performs the merge in the browser. Other PDF168 tools have different processing modes; read the label on the tool you use and the privacy information before handling sensitive documents.
FAQ
Why is the Merge PDFs button disabled?
Add at least two PDF files. A single file does not enable merging; to rearrange its pages, use Organize PDF.
Does merging make every page the same size?
No. The merge operation copies pages with their existing dimensions. A mixture of A4, Letter and landscape pages remains a mixture in the output.
Can I change the order of individual pages?
The ▲ and ▼ buttons move whole files. Extract only the pages you need before merging, or use Organize PDF to reorder pages afterward.