LibreOffice Writer can be used to create fillable PDF forms, being a great free, open source alternative to Adobe’s Acrobat for this use case. LibreOffice is cross-platform too, so you can use it not only on Windows and macOS, but also on Linux. This article explains how to use LibreOffice Writer to create a PDF with fillable forms (interactive forms), with instructions for creating a few common form elements, like adding a text input field, list box (drop-down), option buttons (radio buttons), and a check box, and exporting the document as a PDF form.