Merge PDF
Merge several PDF files into a single document, one after another in the order you choose. Everything runs in your browser, your files are never uploaded.
You can pick several, even in several goes
What merging PDFs is for
Putting several PDFs into a single file is handy to collect receipts and invoices in one document, join the chapters of a thesis or a manual, attach several forms to a single application, or hand in a complete file instead of many separate ones.
The order of the files
The PDFs are merged in the order they appear in the list, which is the order they were loaded. If you need to change the order, clear the list and reload them in the order you want.
The order is the whole job
Merging two PDFs is trivial; the real time goes into the order of the files, because computers list them alphabetically and «page10» comes before «page2». It is the classic trap when selecting a whole folder of scans: the merge works and the document is shuffled.
The remedy that always works is to number the files with leading zeros (01, 02, … 10) before loading them, or to fix the order here by dragging the entries. Once merged, putting the pages back in line costs far more than ordering them first.
What survives a merge and what does not
In the merged file bookmarks and fillable forms are usually lost: the first because they are an index pointing into another document, the second because two different forms can have fields with the same name, and no automatic choice is the right one.
Digital signatures are always invalidated, and that is correct behaviour: a signature certifies that exact file, and a different file is no longer the one that was signed. If you need to merge signed documents, keep the originals and use the merge only as a reading copy.
The size is not the sum of the sizes
The merged file can weigh less than the sum of its pieces, because identical fonts and images are written only once. Across a series of documents generated by the same program, with the same logo at the top, the saving can reach 20%.
It can also weigh more than expected if each piece brings different embedded fonts. If the result is too heavy for an email or a portal, compress it after merging rather than before: compressing ten files one by one is more work and achieves less.
Nearby tools
The opposite direction is in Split PDF and, if you need to stay under a size, in Split a PDF by size. To reorder or remove pages inside a single file there is Organise PDF.