FillOutAForm can either convert a PDF file to a BMP file and then open it (using the free GhostScript program), or open a BMP file you obtained by scanning a paper form. You can scroll the form with your mouse, enter data anywhere on the form, edit an entry, move it, or delete it. And then print it with your entries (which are saved and put on the form when you open it again). You can enter simple arithmetic formulas that can reference other entries (the result shows).
Version 2.93 added Landscape orientation editing and works with any Ghostscript version past 8.0.