Why your answers don't copy across by themselves
Copying and pasting from one PDF into another usually fails. Each form stores its answers against its own hidden field names and layout, so a new copy has nowhere to put what you typed in the old one. Retyping is the usual fallback, and it is slow and easy to get wrong. RepeatForm does the matching for you, then shows you the result before you download anything.
If you have used Acrobat-style export and import of form data, that only works when both files use the same field names.