Create fallback fonts as needed.
If a PDF form field value uses a font that is not in the resources dictionary, a warning is logged and the field value is ignored/not displayed. It's unclear whether this behavior is strictly valid based on the PDF spec (since typically font references, even to base fonts, require a corresponding font dictionary) but Acrobat seems to display the content anyway.
I'm attaching an example PDF I made from some public form. SampleForm-1.pdf
This is a suggested fix using the
createAnnotDrawFont functionality already present in Annot.cc for making standard fonts. I am not very experienced with this codebase so I'm sure I may be making some mistakes!