Hi, can use a PDF document that is already made to put fields in it to be able to fill them with data from the database
Nope, PDFDocument can’t open (parse) PDF files already created. The main class and all the related classes just allow by now creating new PDF documents from scratch on Desktop, Web and iOS.
Yes. Check out DynaPDF (with Lite or Pro license) to import a PDF and use form functions to list existing fields, pick one and read/write the text values.
See acroform/Fill value example file.
Or simply create a brand new pdf with everything you need.