How to compare an original pdf with the signed version
- Step 1Upload the original (unsigned) PDF — Drop the version sent for signing into the diff tool.
- Step 2Upload the signed PDF — Drop the received signed version alongside.
- Step 3Run the comparison — Review all differences between the two versions.
- Step 4Verify that only signature fields changed — If only signature placeholder text changed, the document is unaltered. Investigate any other text differences.
Frequently asked questions
Does this verify the digital signature cryptographically?+
No — PDF diff compares text content only. For cryptographic signature verification, open the PDF in Acrobat and check the digital signature validation status.
What if the signed PDF has a different file size?+
Digital signature data adds to the file size. A difference in file size alone does not indicate content changes — use the diff tool to check text differences.
Can the tool detect if a signature image was added without a digital certificate?+
An image-only signature (a scanned signature image pasted into the PDF) will show as added image content. The diff detects the image addition but cannot verify its authenticity.
Privacy first
All PDF processing runs locally in your browser using PDF-lib and pdf.js. No file is ever uploaded — only metadata counters are saved for signed-in dashboard stats.