Sign PDF API for Developers

    Feature

    Stamp signature images or text-based signatures onto PDFs with precise positioning control.

    Use cases

    Where Sign PDF helps

    • Stamp approval signatures on contracts
    • Add typed signatures for internal reviews
    • Apply "APPROVED" / "REJECTED" stamps with date
    • Overlay signature images on every page
    • Automate sign-off flows in no-code pipelines
    Two signature modes:
    • Image: Upload a signature image (PNG/JPG/WebP with transparency)
    • Text: Provide text to render as a signature with color and size control
    Sign PDF with text signature — copy-paste into your stack
    curl -X POST https://pdfapihub.com/api/v1/sign-pdf \
  -H "CLIENT-API-KEY: your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
  "pdf_url": "https://example.com/contract.pdf",
  "sign_text": "John Smith",
  "sign_color": "#1a0dab",
  "font_size": 42,
  "position": "bottom-right",
  "output_format": "url"
}'

    Parameters

    pdf_url / file
    required

    PDF to sign — URL, upload, or base64.

    signature_url / signature
    conditional

    Signature image URL or upload. Required if sign_text not provided.

    sign_text
    conditional

    Text to render as signature. Required if no image provided.

    sign_color
    optional

    Hex color for text signature. Default #000000.

    font_size
    optional

    Font size for text signature (points). Default 48.

    date_stamp
    optional

    Append current UTC date below signature text.

    page
    optional

    Page number (1-based). Defaults to last page.

    all_pages
    optional

    Stamp on every page.

    position
    optional

    bottom-right (default), bottom-left, top-right, top-left, center, bottom-center, top-center.

    x / y
    optional

    Exact coordinates (PDF points). Overrides position preset.

    width / height
    optional

    Signature dimensions. Defaults: 28% page width, proportional height.

    opacity
    optional

    0.0–1.0 (default 1.0). Lower values for stamp/watermark style.

    output_format
    optional

    file / url / base64 / both

    Sandbox

    Sign a PDF with text or image signature

    Result

    Preview, response, and cURL command