Combining filled-in copies of the same form usually goes wrong: every page shows the first person's answers, or the fields stop being fillable. Drop the filled PDFs here. You'll see which field names they share, then you can merge them so each copy keeps its own answers and stays fillable, or lock the answers in by flattening. Forms often hold personal data, so nothing is uploaded: it all runs in your browser.
// Your merged PDF will appear here
A PDF form field is identified by its name, such as applicant.name, and a field holds exactly one value. The boxes you see on the page are only places where that field is displayed. A form that repeats your name on page 1 and page 5 relies on this. Ten filled copies of the same form contain ten fields that all have the same name. Most combine tools, Acrobat's included, treat same-named fields as one field, so the merged file holds one value and shows it in every copy. Typing into one box then changes all of them. Why combining filled PDF forms changes the answers goes through the mechanism, and the other common failure, where the merged file looks filled in but nothing can be edited.
applicant.name in w9-alice.pdf becomes w9-alice_applicant.name. The answers stay as they were, and every field stays editable. Use this when someone still needs to check or correct the forms after merging.Mergers handle forms in one of two ways, and both cause trouble. Tools that copy pages one by one bring the visible boxes across but not the document's form, so the result looks filled in but nothing is fillable anymore. Tools that copy the form join same-named fields, which produces the "everyone has the first person's answers" problem. A few services can rename fields too, but they need the files uploaded to their servers, which is a poor fit for tax forms, applications and medical paperwork.
It lists every field name that appears in more than one of your files, with the number of files that contain it. These are exactly the fields that would collide under "Keep names". With the default option they're renamed apart, so the list is a preview of what would have gone wrong.
Merging creates a new document, so a digital signature from a source file won't verify in the merged file, whichever option you pick. The tool flags files that contain signature fields. Merge signed copies only for reading, and keep the signed originals as the record.
That's an XFA form, built with Adobe LiveCycle or Designer. Most XFA forms carry an ordinary form underneath, and that is what this tool keeps. "Dynamic" XFA forms that exist only as XFA have nothing underneath for a browser-based tool to read, so the tool flags them. For those, print each one to PDF from Adobe Reader first, then merge the printed copies.
No. Files are read and merged with the open-source pdf-lib library inside your browser. You can check the Network tab in your browser's developer tools while it runs. For merging without forms, plus compression, use the bulk PDF merge & compress tool, which now keeps form fields fillable and separate in the same way.