pdf-editing

PDF Editing Skill

CRITICAL RULES - READ FIRST

NEVER DO THESE:

• NEVER use strikethrough lines to cross out text
• NEVER rasterize or flatten the PDF to images
• NEVER convert PDF pages to PNG/JPG and draw on them
• NEVER use pdf-to-image-to-pdf workflows
• NEVER use add_redact_annot() with BLACK fill (use WHITE fill instead)
• NEVER add text NEXT TO old values - REPLACE them at the SAME position

TWO APPROACHES - CHOOSE THE RIGHT ONE:

1. For REPLACING text (e.g., updating name, email, DOB):

   • Use draw_rect() with white fill to cover old text
   • Use insert_text() at the SAME position
   • Text layer is preserved

2. For TRUE REDACTION of sensitive data (e.g., student ID):

   • Use add_redact_annot(rect, fill=(1,1,1)) with WHITE fill
   • Call apply_redactions() to REMOVE text from PDF structure
   • Then insert_text() to add masked value (e.g., "****5678")
   • Original text is completely removed, not just covered

Overview

USE PYTHON WITH PyMuPDF (fitz) - it is pre-installed and produces the best results.

PyMuPDF preserves the text layer properly, making text extractable after editing. JavaScript libraries like pdf-lib may create text that tools like pypdf cannot extract.

# PyMuPDF is already installed - just use it
python3 -c "import fitz; print('PyMuPDF ready')"

Reading PDF Content

import fitz

doc = fitz.open("input.pdf")
page = doc[0]

# Extract all text to understand the document
text = page.get_text()
print(text)

Finding Text Positions

# search_for() returns list of rectangles where text is found
rects = page.search_for("Label Text")
if rects:
    rect = rects[0]
    # rect.x0, rect.y0 = top-left corner
    # rect.x1, rect.y1 = bottom-right corner
    print(f"Found at: ({rect.x0}, {rect.y0}) to ({rect.x1}, {rect.y1})")

Inserting Text

# Insert text at a specific position
page.insert_text(
    (x_position, y_position),  # coordinates
    "text to insert",
    fontsize=11,
    color=(0, 0, 0)  # black
)

doc.save("output.pdf")