pdflib-impl-form-filling

Automating PDF form filling with JavaScript involves loading an existing template, enumerating field names, and programmatically populating text fields, checkboxes, radios, and dropdowns using pdf-lib. You must update field appearances after setting values to ensure correct rendering.

Filling Unicode text in a PDF form using pdf-lib requires embedding custom Unicode fonts into the document. Standard fonts do not support non-Latin characters, so you must load and register a Unicode-compatible font file before populating your text fields.

Filled PDF form fields may not display values correctly if field appearances are not updated after setting values. When populating text fields or checkboxes with pdf-lib, you must explicitly trigger an appearance update to ensure the viewer renders the changes.

Enumerating PDF form field names before filling them prevents guessing and mapping data incorrectly. The best approach is to load the PDF, access the form structure, and list all field names to create an accurate data map for text fields, checkboxes, and radios.

You can flatten a PDF form after filling it with pdf-lib to lock the entered values permanently. Flattening converts the populated text fields, checkboxes, and dropdowns into static content, or you can save the document as an editable template without flattening.

pdf-lib supports filling dropdowns and radio buttons in PDF forms alongside standard text fields and checkboxes. You can programmatically select options and update their appearances to ensure deterministic rendering across different PDF viewers.