doc: inital commit for PDF generation ADR

[jugglingdev]

Please comment below to add to the discussion regarding a solution to generate and store PDFs.

[jugglingdev]

Important notes when working with pdftk:

pdftk works with form fields defined in AcroForm in PDF. Use the following command to view the field types of your fillable PDF:

pdftk your-form.pdf dump_data_fields_utf8

The FieldTypes recognized by pdftk are:

1. Text - single-line or multi-line text including names and dates
2. Button - distinguish checkboxes and radios with FieldFlags:
   • 32768 (Checkbox, toggled on/off)
   • 49152 (Radio Button, mutually exclusive group)
   • 65536 (Push button, used for image field overlays like signatures)
3. Choice - dropdown or multi-select list
4. Sig - digital signature field

SIGNATURES: pdftk cannot fill the Sig FieldType; it is display-only. Sig requires an actual cryptographic digital signature and is intended for use in tools like Adobe Sign or DocuSign.

CIRCLES: Visual-only elements (like drawings, annotations, and circles) do not appear as FieldTypes. They’re part of the page content, not AcroForm fields. They must be stamped onto the PDF by manually grabbing their coordinates. This applies to the Ethnicity field.