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BytesAgain › Skills › EPUB ↔ PDF Converter
🦀 ClawHub

EPUB ↔ PDF Converter

by @bunsdev

Convert EPUB ↔ PDF bidirectionally. EPUB→PDF preserves layout for analysis; PDF→EPUB compresses and reflows for distribution and ereaders.

Versionv1.1.0
Downloads475
#legal
TERMINAL
clawhub install epub-to-pdf

📖 About This Skill

name: "epub" description: "Convert EPUB ↔ PDF bidirectionally. EPUB→PDF preserves layout for analysis; PDF→EPUB compresses and reflows for distribution and ereaders."

EPUB Skill

When to use

EPUB → PDF

  • Convert EPUB books, papers, or distributed documents to PDF for reading and analysis
  • Preserve layout and formatting before text extraction via pdftoppm
  • Archive EPUB content in a fixed-layout format
  • Prepare EPUBs for downstream processing (rendering, analysis, synthesis)

    • PDF → EPUB

  • Convert papers and PDFs to reflowable EPUB format for ereader distribution
  • Compress PDFs into smaller, device-friendly EPUB archives
  • Auto-detect chapters and structure for better reading experience
  • Redistribute research materials in open formats

    • Workflow

    EPUB → PDF (for analysis)

    1. Check for calibre → install if missing (brew install calibre) 2. Convert EPUB → PDF using ebook-convert with formatting options 3. Validate output → confirm PDF rendered correctly 4. Render pages → use pdftoppm to extract visual content 5. Analyze → pass to PDF skill for text extraction and synthesis

    PDF → EPUB (for distribution)

    1. Check for calibre → install if missing 2. Convert PDF → EPUB using ebook-convert with reflowable settings 3. Auto-detect chapters → ebook-convert scans for structure 4. Validate compression → confirm EPUB is smaller than PDF 5. Archive → save EPUB to research/sources/ for distribution or ereader use

    Usage

    EPUB → PDF (basic)

    ebook-convert input.epub output.pdf

    EPUB → PDF (with layout preservation options)

    ebook-convert input.epub output.pdf \
  --pdf-standard-font "sans" \
  --paper-size "a4" \
  --margin-left 20 \
  --margin-right 20 \
  --margin-top 20 \
  --margin-bottom 20 \
  --pdf-mono-family "mono"

    Note: Valid font families are: serif, sans, mono (not Helvetica, etc.)

    PDF → EPUB (basic)

    ebook-convert input.pdf output.epub

    PDF → EPUB (with compression)

    ebook-convert input.pdf output.epub \
  --output-profile "tablet" \
  --paper-size "a4"

    Note: ebook-convert auto-detects chapters from PDFs. Inspect the output EPUB to verify structure.

    In context (Sage workflow)

    #### EPUB → PDF 

    # Convert EPUB to PDF for analysis
ebook-convert "/path/to/input.epub" "/path/to/research/sources/output.pdf"
    Verify and check size
    
ls -lh "/path/to/research/sources/output.pdf"
    Render pages for visual inspection
    
pdftoppm -png "/path/to/research/sources/output.pdf" "/tmp/preview/page"

    #### PDF → EPUB 

    # Convert PDF to EPUB for distribution
ebook-convert "/path/to/input.pdf" "/path/to/research/sources/output.epub"
    Verify compression
    
ls -lh "/path/to/input.pdf" "/path/to/research/sources/output.epub"
    (EPUB will typically be 30-50% of PDF size)

    Dependencies

    System package: 

    # macOS (Homebrew)
brew install calibre
    Ubuntu/Debian
    
sudo apt-get install -y calibre
    Fedora/RHEL
    
sudo dnf install calibre

    calibre includes ebook-convert and supports many formats:

  • Input: EPUB, PDF, MOBI, AZW, AZW3, HTML, TXT, DOCX, ODT
  • Output: EPUB, PDF, MOBI, AZW, AZW3, DOCX, HTML, TXT

    • Output conventions

  • Location: Save files to research/sources/ with descriptive names
  • Naming: Use title or slug: Author-Title.pdf, title-yyyy-mm-dd.epub
  • EPUB→PDF: Check size (>100 KB typical for books)
  • PDF→EPUB: Typically 30-50% of PDF size due to reflowable format
  • Cleanup: Remove temporary files after verification

    • Quality checks

    After EPUB → PDF:

    1. File exists and readable 2. File size >100 KB (suspiciously small = text-only, may have lost images) 3. file output.pdf confirms it's a valid PDF 4. pdftoppm renders first page successfully

    After PDF → EPUB:

    1. File exists and readable 2. File size is 30-50% of original PDF (good compression ratio) 3. Unzip the EPUB and inspect content.opf for auto-detected chapters 4. Open in ereader or calibre viewer to verify reflowable layout

    Troubleshooting

    EPUB → PDF crashes or produces empty output

  • Check if EPUB is corrupt: unzip -t input.epub
  • Try without formatting options: ebook-convert input.epub output.pdf
  • If EPUB has missing stylesheets (common), calibre will warn but continue
  • Last resort: extract text from EPUB (unzip -p input.epub | grep -r "html") and convert to markdown

    • PDF → EPUB produces wrong chapter detection

  • Run with --verbose to see what calibre detected: ebook-convert input.pdf output.epub --verbose
  • For scanned PDFs (images), conversion may fail or produce text-only EPUB
  • Use pdftotext first to extract text, then create EPUB from markdown

    • File size issues

  • EPUB→PDF: if output is <50 KB, likely text-only (no images captured)
  • PDF→EPUB: if output is >150% of input, likely includes images; use --output-profile "tablet" for better compression

    • Notes

  • Layout preservation (EPUB→PDF): ebook-convert maintains structure, typography, images
  • Reflowable format (PDF→EPUB): EPUB reflows to device width; fixed-layout PDFs may lose structure
  • Chapter detection (PDF→EPUB): Automatic; works best on PDFs with clear page breaks or bookmarks
  • Scanned PDFs: May fail or produce text-only output (no OCR)
  • Large files: Some books convert to large files (100+ MB PDFs/EPUBs). Normal.

    • When conversion fails

  • EPUB is corrupt: unzip -t input.epub (EPUBs are ZIP files)
  • Verbose output: ebook-convert input.epub output.pdf --verbose for error details
  • Unsupported format: Request original source in different format
  • Manual fallback: Extract text from EPUB or PDF, save as markdown, document the failure

    • Related

  • PDF Skill — for reading and rendering converted PDFs
  • pdftotext — text extraction from PDF
  • Calibre Handbook: https://manual.calibre-ebook.com/

    • Tested Conversions

    ✅ SHELLFISH.epub → SHELLFISH.pdf (73 KB → 639 KB, layout preserved, 89 pages) ✅ SHELLFISH.pdf → SHELLFISH-test.epub (639 KB → 262 KB, chapters auto-detected, 24 parts)

    _EPUB ↔ PDF bidirectional conversion pipeline ready._ _Last tested: 2026-04-29 | Calibre v5.x_

    ⚡ When to Use

    TriggerAction
    - Convert EPUB books, papers, or distributed documents to PDF for reading and analysis
    - Preserve layout and formatting before text extraction via pdftoppm
    - Archive EPUB content in a fixed-layout format
    - Prepare EPUBs for downstream processing (rendering, analysis, synthesis)
    ### PDF → EPUB
    - Convert papers and PDFs to reflowable EPUB format for ereader distribution
    - Compress PDFs into smaller, device-friendly EPUB archives
    - Auto-detect chapters and structure for better reading experience
    - Redistribute research materials in open formats

    💡 Examples

    EPUB → PDF (basic)

    ebook-convert input.epub output.pdf

    EPUB → PDF (with layout preservation options)

    ebook-convert input.epub output.pdf \
  --pdf-standard-font "sans" \
  --paper-size "a4" \
  --margin-left 20 \
  --margin-right 20 \
  --margin-top 20 \
  --margin-bottom 20 \
  --pdf-mono-family "mono"

    Note: Valid font families are: serif, sans, mono (not Helvetica, etc.)

    PDF → EPUB (basic)

    ebook-convert input.pdf output.epub

    PDF → EPUB (with compression)

    ebook-convert input.pdf output.epub \
  --output-profile "tablet" \
  --paper-size "a4"

    Note: ebook-convert auto-detects chapters from PDFs. Inspect the output EPUB to verify structure.

    In context (Sage workflow)

    #### EPUB → PDF 

    # Convert EPUB to PDF for analysis
ebook-convert "/path/to/input.epub" "/path/to/research/sources/output.pdf"
    Verify and check size
    
ls -lh "/path/to/research/sources/output.pdf"
    Render pages for visual inspection
    
pdftoppm -png "/path/to/research/sources/output.pdf" "/tmp/preview/page"

    #### PDF → EPUB 

    # Convert PDF to EPUB for distribution
ebook-convert "/path/to/input.pdf" "/path/to/research/sources/output.epub"
    Verify compression
    
ls -lh "/path/to/input.pdf" "/path/to/research/sources/output.epub"
    (EPUB will typically be 30-50% of PDF size)

    📋 Tips & Best Practices

  • Layout preservation (EPUB→PDF): ebook-convert maintains structure, typography, images
  • Reflowable format (PDF→EPUB): EPUB reflows to device width; fixed-layout PDFs may lose structure
  • Chapter detection (PDF→EPUB): Automatic; works best on PDFs with clear page breaks or bookmarks
  • Scanned PDFs: May fail or produce text-only output (no OCR)
  • Large files: Some books convert to large files (100+ MB PDFs/EPUBs). Normal.