Convert PDFs for Kindle Direct Publishing (KDP)

KDP has two completely different submission paths: print (paperback/hardcover) which requires a precisely sized print-ready PDF, and eBook (Kindle) which uses reflowable EPUB. Most conversion mistakes come from authors treating a screen PDF as a print PDF, or trying to submit a print PDF as an ebook. This guide covers both paths with exact specs.

KDP print PDF: exact specifications

Per KDP's manuscript formatting guide:

Print (Paperback / Hardcover)

• File format: PDF, version 1.3–1.7. PDF/X-1a is recommended (pre-press standard, ensures print accuracy).
• Page size: Exact trim size + 0.125 inch bleed on all exterior edges. Example: for a 6×9 book, each page must be 6.25 × 9.25 inches (trim size + bleed on all sides). No bleed on spine edge.
• Image resolution: 300 DPI minimum. Images below 300 DPI will look soft or pixelated in print. 600 DPI for line art and text elements.
• Color: CMYK for color books. Grayscale for black-and-white books (KDP will convert RGB to grayscale but conversion quality varies — do it yourself).
• Fonts: All fonts must be embedded. Fonts not embedded cause KDP's preflight checker to reject the file.
• Margins: Minimum 0.25 inch all sides. If page count > 300, inside (gutter) margin must be at least 0.75 inch to account for binding.
• Max file size: 650 MB. In practice, keep under 100 MB.

eBook (Kindle)

• Submit EPUB 3.0 (preferred) or MOBI. KDP Convert accepts DOCX, HTML, or EPUB.
• Do NOT submit a print PDF as a Kindle ebook — it renders as a fixed-layout document that looks broken on most devices. Only use PDF for fixed-layout children's books or illustrated books (see KDP's fixed-layout guide).

Common KDP trim sizes (page dimensions with bleed)

Note: "bleed" means content extends 0.125 inch beyond the trim edge. Use it for background colors and images that go to the page edge. If your content has white margins, bleed is still required in the PDF but the bleed area will be trimmed white.

Conversion commands (curl + Python)

Converting a Word document or HTML manuscript to PDF:

# curl — convert DOCX manuscript to PDF
curl -X POST https://changethisfile.com/v1/convert \
  -H "Authorization: Bearer ctf_sk_your_key_here" \
  -F "file=@manuscript.docx" \
  -F "target=pdf" \
  -o manuscript.pdf

import requests
from pathlib import Path

API_KEY = "ctf_sk_your_key_here"

def convert_manuscript_to_pdf(in_path: str, out_path: str) -> None:
    """Convert manuscript file to PDF for KDP."""
    with open(in_path, "rb") as f:
        resp = requests.post(
            "https://changethisfile.com/v1/convert",
            headers={"Authorization": f"Bearer {API_KEY}"},
            files={"file": f},
            data={"target": "pdf"},
            timeout=120,
        )
    resp.raise_for_status()
    Path(out_path).write_bytes(resp.content)
    print(f"PDF saved: {out_path}")

# Convert DOCX to PDF
convert_manuscript_to_pdf("manuscript.docx", "manuscript-for-kdp.pdf")

For ebook conversion (DOCX or EPUB → Kindle-compatible):

# Convert DOCX to EPUB for Kindle Direct Publishing ebook
curl -X POST https://changethisfile.com/v1/convert \
  -H "Authorization: Bearer ctf_sk_your_key_here" \
  -F "file=@manuscript.docx" \
  -F "target=epub" \
  -o manuscript.epub

Note: The generated PDF from a DOCX is screen-resolution (72 DPI equivalent for text, which prints fine as vector text). For books with embedded photographs, images must be 300 DPI — use a desktop publishing tool (InDesign, Affinity Publisher) to set up the print-ready PDF for best results. The API handles straightforward text-heavy manuscripts.

Batch script: convert all chapters for anthology

#!/usr/bin/env bash
# Usage: ./convert_kdp_batch.sh ./chapters ./pdf-chapters
# Converts all DOCX/ODT files to PDF (for later merge with pdftk/ghostscript)

API_KEY="ctf_sk_your_key_here"
INPUT_DIR="${1:-.}"
OUTPUT_DIR="${2:-./pdf-chapters}"

mkdir -p "$OUTPUT_DIR"
success=0; failed=0

for doc in "$INPUT_DIR"/*.{docx,DOCX,odt,ODT,rtf}; do
  [ -f "$doc" ] || continue
  base=$(basename "$doc" | sed 's/\.[^.]*$//')
  out="$OUTPUT_DIR/${base}.pdf"

  printf "%-50s" "$(basename $doc)..."
  code=$(curl -s -o "$out" -w "%{http_code}" \
    -X POST https://changethisfile.com/v1/convert \
    -H "Authorization: Bearer $API_KEY" \
    -F "file=@$doc" \
    -F "target=pdf")

  if [ "$code" = "200" ]; then
    pages=$(pdfinfo "$out" 2>/dev/null | grep Pages | awk '{print $2}' || echo "?")
    echo "OK (${pages} pages)"
    ((success++))
  else
    echo "FAILED (HTTP $code)"
    ((failed++))
  fi
done

echo ""
echo "$success converted, $failed failed"
echo "To merge: pdftk $OUTPUT_DIR/*.pdf cat output combined-manuscript.pdf"

Common KDP submission rejections

• Non-embedded fonts. KDP's preflight checker rejects PDFs with non-embedded fonts. In Microsoft Word, use File → Options → Save → check "Embed fonts in the file". In InDesign, use PDF/X-1a preset which forces font embedding.
• Wrong page size. The #1 cause of print-through misalignment. Your PDF pages must be trim size + 0.125 inch on all sides. If you export from Word at Letter size (8.5×11) but your book is 6×9, KDP will reject or scale incorrectly.
• Images under 300 DPI. Downloaded images from the web are typically 72–96 DPI. These look fine on screen but will be visibly soft in print. Use 300 DPI images for all interior illustrations and photos.
• RGB images in B&W books. KDP converts RGB to grayscale, but the conversion can look muddy — especially for photos. Convert images to true grayscale yourself before embedding.
• Submitting print PDF as Kindle ebook. A print PDF submitted as a Kindle ebook will show as a fixed-layout document — unreadable on Kindle Paperwhite and Kindle app. Submit EPUB for reflowable ebooks, or use KDP's fixed-layout tool for illustrated books.
• Spine width calculation. The spine of your cover must match the page count. KDP provides a cover template calculator — wrong spine width causes rejection. Use their Cover Calculator.

Cover PDF specifications

KDP covers are a single-page PDF wrapping the spine — not separate front/back files:

• Includes: Back cover, spine, and front cover as one flat PDF
• Resolution: 300 DPI minimum
• Color space: CMYK or RGB (KDP accepts both; CMYK is safer for color accuracy)
• Bleed: 0.125 inch on all exterior edges
• Spine width: Calculated from page count and paper type — use KDP's Cover Calculator
• Format: PDF/X-1a or PDF 1.3–1.7

Cover PDF is a separate upload from the interior manuscript PDF in KDP's upload flow.

KDP print PDFs have more precision requirements than any other PDF workflow. The non-negotiables are: correct page size (trim + bleed), embedded fonts, and 300 DPI images. Get these right before uploading and KDP's preflight checker will clear in minutes instead of cycling through rejections. Free tier covers 1,000 conversions/month.