PDF Processing Guide

Comprehensive PDF processing operations using Python libraries and command-line tools.

When to Use

Use This Skill When

• 需要提取PDF中的文本或表格数据
• 合并多个PDF文件为一个
• 将PDF拆分为单页文件
• 旋转PDF页面方向
• 为PDF添加水印
• 创建新的PDF文档
• 处理PDF表单填写
• 对PDF进行加密或解密
• OCR识别扫描版PDF
• 从PDF中提取图片

Do NOT Use This Skill If

• PDF文件被密码保护且无密码
• 需要复杂的PDF编辑（如修改现有内容）
• PDF文件损坏无法读取
• 需要保留原始PDF的复杂排版

Typical Trigger Phrases

Chinese:

• "提取PDF文字"
• "合并PDF文件"
• "拆分PDF"
• "PDF加水印"
• "PDF转Word"
• "扫描PDF识别"

English:

• "Extract PDF text"
• "Merge PDF files"
• "Split PDF"
• "Add watermark to PDF"
• "Convert PDF to Word"
• "OCR scanned PDF"

Workflow

Step 1: 确定PDF操作类型

Step 2: 选择合适工具

• pypdf: 基础操作（合并、拆分、元数据）
• pdfplumber: 文本和表格提取
• reportlab: 创建PDF
• qpdf: 命令行高级操作

Step 3: 执行操作

from pypdf import PdfReader, PdfWriter
# 或
import pdfplumber

Step 4: 验证结果

• 检查输出文件完整性
• 验证提取的文本/数据准确性
• 确认格式保持正确

Guardrails

Anti-Patterns

• ❌ 使用Unicode上下标字符（会导致黑框）
• ❌ 不验证提取的表格数据
• ❌ 忽略PDF版本兼容性问题
• ❌ 处理大型PDF时不分页处理

Limitations

• 扫描版PDF需要OCR才能提取文本
• 复杂排版可能丢失格式
• 某些PDF字体嵌入问题
• 加密PDF需要密码

Important Notes

1. Subscripts/Superscripts: 使用

   <sub>

   和

   <super>

   标签，不要用Unicode字符
2. Table Extraction: 复杂表格可能需要手动调整
3. OCR Quality: 依赖图片清晰度

Quick Start

from pypdf import PdfReader, PdfWriter

# Read a PDF
reader = PdfReader("document.pdf")
print(f"Pages: {len(reader.pages)}")

# Extract text
text = ""
for page in reader.pages:
    text += page.extract_text()

Python Libraries

pypdf - Basic Operations

Merge PDFs

from pypdf import PdfWriter, PdfReader

writer = PdfWriter()
for pdf_file in ["doc1.pdf", "doc2.pdf", "doc3.pdf"]:
    reader = PdfReader(pdf_file)
    for page in reader.pages:
        writer.add_page(page)

with open("merged.pdf", "wb") as output:
    writer.write(output)

Split PDF

reader = PdfReader("input.pdf")
for i, page in enumerate(reader.pages):
    writer = PdfWriter()
    writer.add_page(page)
    with open(f"page_{i+1}.pdf", "wb") as output:
        writer.write(output)

Extract Metadata

reader = PdfReader("document.pdf")
meta = reader.metadata
print(f"Title: {meta.title}")
print(f"Author: {meta.author}")

Rotate Pages

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

page = reader.pages[0]
page.rotate(90)  # Rotate 90 degrees clockwise
writer.add_page(page)

with open("rotated.pdf", "wb") as output:
    writer.write(output)

pdfplumber - Text and Table Extraction

Extract Text with Layout

import pdfplumber

with pdfplumber.open("document.pdf") as pdf:
    for page in pdf.pages:
        text = page.extract_text()
        print(text)

Extract Tables

with pdfplumber.open("document.pdf") as pdf:
    for i, page in enumerate(pdf.pages):
        tables = page.extract_tables()
        for j, table in enumerate(tables):
            print(f"Table {j+1} on page {i+1}:")
            for row in table:
                print(row)

Advanced Table Extraction

import pandas as pd

with pdfplumber.open("document.pdf") as pdf:
    all_tables = []
    for page in pdf.pages:
        tables = page.extract_tables()
        for table in tables:
            if table:
                df = pd.DataFrame(table[1:], columns=table[0])
                all_tables.append(df)

if all_tables:
    combined_df = pd.concat(all_tables, ignore_index=True)
    combined_df.to_excel("extracted_tables.xlsx", index=False)

reportlab - Create PDFs

Basic PDF Creation

from reportlab.lib.pagesizes import letter
from reportlab.pdfgen import canvas

c = canvas.Canvas("hello.pdf", pagesize=letter)
width, height = letter

c.drawString(100, height - 100, "Hello World!")
c.line(100, height - 140, 400, height - 140)

c.save()

Multi-Page PDF

from reportlab.platypus import SimpleDocTemplate, Paragraph, Spacer, PageBreak
from reportlab.lib.styles import getSampleStyleSheet

doc = SimpleDocTemplate("report.pdf", pagesize=letter)
styles = getSampleStyleSheet()
story = []

story.append(Paragraph("Report Title", styles['Title']))
story.append(Spacer(1, 12))
story.append(Paragraph("Body content", styles['Normal']))
story.append(PageBreak())
story.append(Paragraph("Page 2", styles['Heading1']))

doc.build(story)

Subscripts and Superscripts

IMPORTANT: Never use Unicode subscript/superscript characters. Use ReportLab's XML markup:

from reportlab.platypus import Paragraph

# Subscripts: use <sub> tag
chemical = Paragraph("H<sub>2</sub>O", styles['Normal'])

# Superscripts: use <super> tag  
squared = Paragraph("x<super>2</super>", styles['Normal'])

Command-Line Tools

pdftotext (poppler-utils)

# Extract text
pdftotext input.pdf output.txt

# Preserve layout
pdftotext -layout input.pdf output.txt

# Specific pages
pdftotext -f 1 -l 5 input.pdf output.txt  # Pages 1-5

qpdf

# Merge PDFs
qpdf --empty --pages file1.pdf file2.pdf -- merged.pdf

# Split pages
qpdf input.pdf --pages . 1-5 -- pages1-5.pdf

# Rotate pages
qpdf input.pdf output.pdf --rotate=+90:1

# Remove password
qpdf --password=mypassword --decrypt encrypted.pdf decrypted.pdf

Common Tasks

OCR on Scanned PDFs

import pytesseract
from pdf2image import convert_from_path

images = convert_from_path('scanned.pdf')
text = ""
for i, image in enumerate(images):
    text += f"Page {i+1}:\n"
    text += pytesseract.image_to_string(image)
    text += "\n\n"

Add Watermark

from pypdf import PdfReader, PdfWriter

watermark = PdfReader("watermark.pdf").pages[0]
reader = PdfReader("document.pdf")
writer = PdfWriter()

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

with open("watermarked.pdf", "wb") as output:
    writer.write(output)

Extract Images

pdfimages -j input.pdf output_prefix

Password Protection

from pypdf import PdfReader, PdfWriter

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

for page in reader.pages:
    writer.add_page(page)

writer.encrypt("userpassword", "ownerpassword")

with open("encrypted.pdf", "wb") as output:
    writer.write(output)

Quick Reference

writer.add_page(page)

page.extract_text()

page.extract_tables()

qpdf --empty --pages ...

Related Skills

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