Have you used online tax preparation software or similar form preparation tools before? (In the U.S., TurboTax and FAFSA on the Web are two well-known examples.)
These tools guide the user through web-based forms and collect their information. At the end, they provide them with a pre-filled copy of a PDF form containing the same information.
FillPDF lets you build this kind of workflow.
Through the magic of the Token and Webform Tokens modules, it is possible to indicate which fields on your website represent which FillPDF fields. When a user goes to a special link on your site, the module does its job, and the PDF is provided as a downloadable file.*
* You can also save the PDF to a file, save it and provide it as a download, or send the user directly to the saved PDF file.
Why not just generate a PDF?
If you have tried generating PDFs in PHP before, you may already know what I'm going to say. If not, read on.
In many situations, a PDF template is provided by an agency, and its format is strict. This is common in government, law, commercial real estate, the mortgage industry, finances, and other industries. FillPDF is an excellent option if you are in such a situation. This is because it is often difficult to get a generated PDF to look the same as is desired.
If you do want to generate a PDF from scratch, check out Printer, e-mail, and PDF versions's PDF generation module, which uses one of several PDF generation tools to print a page as it looks in its printer-friendly view.