pdf-processing

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Use when the user needs PDF generation, manipulation, form filling, table extraction, OCR, merging, splitting, watermarking, or metadata handling. Trigger conditions: generate PDF reports, extract text or tables from PDFs, fill PDF forms programmatically, merge or split PDF files, add watermarks, OCR scanned documents, read or write PDF metadata, convert HTML to PDF.

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npx skill4agent add pixel-process-ug/superkit-agents pdf-processing

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PDF Processing

Overview

Generate, manipulate, and extract data from PDF documents. This skill covers the Python PDF ecosystem: pypdf for merging/splitting/metadata, pdfplumber for text and table extraction, reportlab for generation, pytesseract for OCR, and strategies for form filling, watermarking, and complex document assembly.
Apply this skill whenever PDFs need to be created, parsed, transformed, or combined through code.

Multi-Phase Process

Phase 1: Requirements

  1. Determine operation type (generate, extract, manipulate)
  2. Identify input PDF characteristics (scanned, digital, forms)
  3. Define output requirements (format, quality, size)
  4. Plan data pipeline (source data to PDF or PDF to data)
  5. Assess volume and performance requirements
STOP — Do NOT select a library until the operation type and input characteristics are clear.

Phase 2: Implementation

  1. Select appropriate library for the task (see decision table)
  2. Implement core processing logic
  3. Handle edge cases (corrupted files, encrypted PDFs, mixed content)
  4. Add error handling and validation
  5. Optimize for file size and processing speed
STOP — Do NOT skip edge case handling for encrypted, rotated, or scanned PDFs.

Phase 3: Validation

  1. Verify output renders correctly in multiple PDF viewers
  2. Check text is selectable (not rasterized) when applicable
  3. Validate extracted data accuracy
  4. Test with edge case PDFs (large, encrypted, scanned)
  5. Verify accessibility (tagged PDF where needed)

Library Selection Decision Table

TaskLibraryWhyAlternative
Text extractionpdfplumberBest accuracy, handles layoutspypdf (simpler, less accurate)
Table extractionpdfplumberStructured table parsingcamelot (dedicated table tool)
PDF generationreportlabFull control, professional qualityweasyprint (HTML-to-PDF)
Merge / splitpypdfSimple, reliable, fast
Form fillingpypdfReads and fills AcroFormspdfrw (alternative API)
Metadata read/writepypdfRead/write PDF properties
OCR (scanned docs)pytesseract + pdf2imageScanned document text extractionEasyOCR (deep learning)
Watermarkingpypdf + reportlabOverlay pages
HTML to PDFweasyprintCSS-based layout, server-friendlyplaywright (browser rendering)

PDF Generation with ReportLab

python
from reportlab.lib.pagesizes import A4
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.units import cm, mm
from reportlab.lib.colors import HexColor
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table,
    TableStyle, Image, PageBreak
)
from reportlab.lib import colors

def generate_report(output_path, data):
    doc = SimpleDocTemplate(
        output_path,
        pagesize=A4,
        topMargin=2.5*cm,
        bottomMargin=2.5*cm,
        leftMargin=2.5*cm,
        rightMargin=2.5*cm,
    )

    styles = getSampleStyleSheet()
    styles.add(ParagraphStyle(
        name='CustomTitle',
        parent=styles['Title'],
        fontSize=24,
        textColor=HexColor('#2F5496'),
        spaceAfter=20,
    ))

    story = []

    # Title
    story.append(Paragraph(data['title'], styles['CustomTitle']))
    story.append(Spacer(1, 12))

    # Body text
    story.append(Paragraph(data['body'], styles['Normal']))
    story.append(Spacer(1, 20))

    # Table
    table_data = [['Name', 'Value', 'Status']]
    for row in data['rows']:
        table_data.append([row['name'], row['value'], row['status']])

    table = Table(table_data, colWidths=[6*cm, 4*cm, 4*cm])
    table.setStyle(TableStyle([
        ('BACKGROUND', (0, 0), (-1, 0), HexColor('#2F5496')),
        ('TEXTCOLOR', (0, 0), (-1, 0), colors.white),
        ('FONTNAME', (0, 0), (-1, 0), 'Helvetica-Bold'),
        ('FONTSIZE', (0, 0), (-1, 0), 11),
        ('ALIGN', (0, 0), (-1, -1), 'CENTER'),
        ('GRID', (0, 0), (-1, -1), 0.5, colors.grey),
        ('ROWBACKGROUNDS', (0, 1), (-1, -1), [colors.white, HexColor('#F0F4FA')]),
        ('TOPPADDING', (0, 0), (-1, -1), 8),
        ('BOTTOMPADDING', (0, 0), (-1, -1), 8),
    ]))
    story.append(table)

    doc.build(story)

Custom Page Template (Headers/Footers)

python
from reportlab.platypus import BaseDocTemplate, Frame, PageTemplate
from datetime import datetime

def add_header_footer(canvas, doc):
    canvas.saveState()
    # Header
    canvas.setFont('Helvetica', 9)
    canvas.setFillColor(HexColor('#888888'))
    canvas.drawString(2.5*cm, A4[1] - 1.5*cm, 'Company Name — Confidential')
    canvas.drawRightString(A4[0] - 2.5*cm, A4[1] - 1.5*cm, f'Page {doc.page}')
    # Footer
    canvas.drawCentredString(A4[0]/2, 1.5*cm, f'Generated on {datetime.now():%Y-%m-%d}')
    canvas.restoreState()

doc = BaseDocTemplate(output_path, pagesize=A4)
frame = Frame(2.5*cm, 2.5*cm, A4[0]-5*cm, A4[1]-5*cm)
doc.addPageTemplates([PageTemplate(id='main', frames=[frame], onPage=add_header_footer)])

Text and Table Extraction

pdfplumber

python
import pdfplumber

with pdfplumber.open('document.pdf') as pdf:
    # Extract text from all pages
    full_text = ''
    for page in pdf.pages:
        full_text += page.extract_text() + '\n'

    # Extract tables
    for page in pdf.pages:
        tables = page.extract_tables()
        for table in tables:
            for row in table:
                print(row)

    # Extract text from specific area
    page = pdf.pages[0]
    bbox = (50, 100, 400, 300)  # (x0, top, x1, bottom)
    cropped = page.within_bbox(bbox)
    text = cropped.extract_text()

Table Extraction Settings

python
table_settings = {
    "vertical_strategy": "lines",    # or "text", "explicit"
    "horizontal_strategy": "lines",
    "snap_tolerance": 3,
    "join_tolerance": 3,
    "edge_min_length": 3,
    "min_words_vertical": 3,
    "min_words_horizontal": 1,
}

tables = page.extract_tables(table_settings)

Form Filling

python
from pypdf import PdfReader, PdfWriter

reader = PdfReader('form.pdf')
writer = PdfWriter()
writer.append(reader)

# Fill form fields
writer.update_page_form_field_values(
    writer.pages[0],
    {
        'full_name': 'Alice Johnson',
        'email': 'alice@example.com',
        'date': '2025-03-15',
        'agree_terms': '/Yes',  # Checkbox
    },
    auto_regenerate=False,
)

with open('filled_form.pdf', 'wb') as f:
    writer.write(f)

OCR (Scanned PDFs)

python
from pdf2image import convert_from_path
import pytesseract

def ocr_pdf(pdf_path, language='eng'):
    images = convert_from_path(pdf_path, dpi=300)
    full_text = ''
    for i, image in enumerate(images):
        text = pytesseract.image_to_string(image, lang=language)
        full_text += f'\n--- Page {i+1} ---\n{text}'
    return full_text

# For better accuracy with specific layouts:
def ocr_with_config(image):
    custom_config = r'--oem 3 --psm 6'  # LSTM engine, assume uniform block
    return pytesseract.image_to_string(image, config=custom_config)

Merge and Split

python
from pypdf import PdfReader, PdfWriter

# Merge multiple PDFs
def merge_pdfs(input_paths, output_path):
    writer = PdfWriter()
    for path in input_paths:
        reader = PdfReader(path)
        for page in reader.pages:
            writer.add_page(page)
    with open(output_path, 'wb') as f:
        writer.write(f)

# Split PDF by page ranges
def split_pdf(input_path, ranges, output_dir):
    reader = PdfReader(input_path)
    for i, (start, end) in enumerate(ranges):
        writer = PdfWriter()
        for page_num in range(start - 1, min(end, len(reader.pages))):
            writer.add_page(reader.pages[page_num])
        with open(f'{output_dir}/part_{i+1}.pdf', 'wb') as f:
            writer.write(f)

# Extract specific pages
def extract_pages(input_path, page_numbers, output_path):
    reader = PdfReader(input_path)
    writer = PdfWriter()
    for num in page_numbers:
        writer.add_page(reader.pages[num - 1])
    with open(output_path, 'wb') as f:
        writer.write(f)

Watermarking

python
from pypdf import PdfReader, PdfWriter
from reportlab.pdfgen import canvas as rl_canvas
from reportlab.lib.pagesizes import A4
from io import BytesIO

def create_watermark(text, opacity=0.1):
    buffer = BytesIO()
    c = rl_canvas.Canvas(buffer, pagesize=A4)
    c.setFillAlpha(opacity)
    c.setFont('Helvetica-Bold', 60)
    c.setFillColorRGB(0.5, 0.5, 0.5)
    c.translate(A4[0]/2, A4[1]/2)
    c.rotate(45)
    c.drawCentredString(0, 0, text)
    c.save()
    buffer.seek(0)
    return PdfReader(buffer)

def apply_watermark(input_path, output_path, watermark_text):
    watermark = create_watermark(watermark_text)
    reader = PdfReader(input_path)
    writer = PdfWriter()

    for page in reader.pages:
        page.merge_page(watermark.pages[0])
        writer.add_page(page)

    with open(output_path, 'wb') as f:
        writer.write(f)

Metadata Handling

python
from pypdf import PdfReader, PdfWriter

# Read metadata
reader = PdfReader('document.pdf')
info = reader.metadata
print(f'Title: {info.title}')
print(f'Author: {info.author}')
print(f'Pages: {len(reader.pages)}')

# Write metadata
writer = PdfWriter()
writer.append(reader)
writer.add_metadata({
    '/Title': 'Updated Title',
    '/Author': 'Author Name',
    '/Subject': 'Document Subject',
    '/Creator': 'My Application',
})
with open('updated.pdf', 'wb') as f:
    writer.write(f)

Anti-Patterns / Common Mistakes

Anti-PatternWhy It FailsWhat To Do Instead
OCR on digital (text-based) PDFsSlow and inaccurate when text is already extractableCheck if text extracts first, OCR only if empty
Not handling encrypted PDFsCrashes or silent failuresDetect encryption, prompt for password or skip gracefully
Loading entire large PDFs into memoryMemory exhaustion on serverStream pages or process in chunks
Ignoring page rotation metadataText extraction returns garbled resultsRead and apply rotation before extraction
Hardcoding page dimensionsBreaks on non-A4 documentsRead dimensions from source PDF
Not closing file handlesResource leaks in long-running processesUse context managers (
with
statements)
Generating without multi-viewer testingRendering differences across viewersTest in Adobe Reader, Preview, and Chrome
Extracting tables without tuning settingsPoor column alignment, merged cellsAdjust
table_settings
per document type

Anti-Rationalization Guards

  • Do NOT use OCR without first attempting direct text extraction -- check the PDF type.
  • Do NOT skip encryption detection -- handle it explicitly even if "most PDFs aren't encrypted."
  • Do NOT assume A4 page size -- read dimensions from the source document.
  • Do NOT test in only one PDF viewer -- rendering varies across Adobe, Preview, and Chrome.
  • Do NOT process large PDFs without memory-conscious patterns (streaming, chunking).

Integration Points

SkillHow It Connects
docx-processing
DOCX-to-PDF conversion pipeline, or choosing between formats
xlsx-processing
Data from Excel populates PDF report tables
email-composer
Generated PDFs attach to professional emails
content-research-writer
Research output formatted as PDF whitepapers
file-organizer
Output file naming and directory structure conventions
deployment
PDF generation pipelines in server/CI environments

Skill Type

FLEXIBLE — Select the appropriate library and approach based on the specific PDF task. ReportLab for generation, pdfplumber for extraction, pypdf for manipulation. Combine as needed.