Pdf form filler

Skill cxcscmu/SkillLearnBench/skills/b4-skill-creator-claude-opus-4-6/court-form-filling/pdf-form-filler

[COLM'26] SkillLearnBench is the first benchmark for evaluating continual learning methods that automatically generate agent skills.

Install

npx -y skills add cxcscmu/SkillLearnBench --skill pdf-form-filler

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What its author says it does

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Fill PDF form fields programmatically using Python and pypdf. Use this skill whenever the user needs to fill out a PDF form, set text fields, or check checkboxes in a PDF document.

SKILL.md

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PDF Form Filler

Fill PDF forms using pypdf (available in the environment).

Workflow

Extract field names: Read the PDF and list all form fields with their full hierarchical paths
Identify field types: /Tx = text field, /Btn = checkbox/button
Map data to fields: Match user-provided data to the correct field paths
Fill and save: Use pypdf.PdfWriter to write values

Key Code Pattern

import pypdf

reader = pypdf.PdfReader("input.pdf")
writer = pypdf.PdfWriter()
writer.append(reader)

# Fill text fields - use the SHORT field name (leaf), not full path
# writer.update_page_form_field_values(writer.pages[page_idx], {"FieldName[0]": "value"})

# For checkboxes, update the annotation directly:
# Find the annotation on the page, then set /V and /AS to the checked state
for page in writer.pages:
    for annot in page.get("/Annots", []):
        obj = annot.get_object()
        if obj.get("/T") == "CheckboxName[0]":
            obj.update({
                pypdf.generic.NameObject("/V"): pypdf.generic.NameObject("/1"),
                pypdf.generic.NameObject("/AS"): pypdf.generic.NameObject("/1"),
            })

writer.write("output.pdf")

Checkbox States

Check the /AP -> /N dictionary for valid appearance states (e.g., /1, /2, /Off)
Set both /V and /AS to the desired state
/Off typically means unchecked

Tips

Field names in annotations use the SHORT leaf name (e.g., PlaintiffName1[0]), not the full hierarchical path
update_page_form_field_values works for text fields on a specific page
For checkboxes, iterate annotations and update directly
Some PDFs have duplicate field names across pages (e.g., Plaintiff[0] on pages 2, 3, 4) - handle each page separately