Merging PDFs copies each page with its fonts and images, so visible content survives unchanged. Bookmarks, internal links and form fields can break, so check them in the result.
What survives a merge
Text, fonts, images, vector graphics, page size and rotation all survive. Pages are copied without re-rendering or re-compression. Password-free PDFs can be combined regardless of what created them.
What can change or break
- Bookmarks: the sidebar outline is stored per document, and many merge tools drop it.
- Internal links: a link to "page 12" may break because page positions shift. External web links usually work.
- Form fields: names must be unique in a document. Merging two copies of a form can mirror duplicate fields (typing in one fills the other), or the tool may rename or flatten them. Filled forms are the most error-prone merge. Flatten them first when you can.
- Printed page numbers: they do not change, so a merged file can contain several "page 1"s. The reader's page counter shows the real sequence.
- Metadata and accessibility tags: title and author are usually reset or taken from the first file. Reading-order tags often do not survive.
Why merged files can be bigger than the sum
Each source may embed its own fonts, so the result can hold several similar font subsets. Large scanned page images also add size.
Merge workflow
- Order the files before merging. Reordering files is easier than reordering pages.
- In the merge tool, add PDFs, drag them into order, untick any to exclude, and download. Nothing is uploaded.
- Delete blank pages and duplicate cover sheets in the page editor, which shows every page as a thumbnail. Removed pages can be restored until you download.
- Scroll the result, test the links and bookmarks you need, and confirm the page count.
To sign the result, use the PDF signing tool. The electronic signatures guide explains the signature types.