Add Seal to PDF Online Free

When this workflow is enough

This workflow is enough for everyday office documents, approval copies, review marks, receipt stamps, and internal PDF circulation where a visible page mark is sufficient.

When this workflow is not enough

It is not enough when you need signer identity verification, certificate validation, notarization, or a legally qualified electronic signature workflow.

Practical guidance

Adding a seal to a PDF online is usually a simple visual workflow: choose the PDF, choose the seal image, preview the page, and export a new copy. The important part is not only whether the seal appears, but whether it appears in a place that still leaves the document readable. A company seal, approval mark, or receipt stamp can easily cover a date, signature line, page number, total amount, or contract clause if it is placed too quickly.

For the cleanest result, use a transparent PNG seal image rather than a JPG. A transparent PNG lets the original PDF content remain visible around and inside the seal. This matters on contracts, invoices, forms, and scanned pages where the seal may overlap printed text or table lines. If your seal image has a white square background, remove the background before stamping or choose a position where the box will not hide important content.

The free browser workflow is most useful for everyday office routing, internal approval copies, draft marks, invoice status labels, and visible review stamps. It is not the right choice when your organization requires verified signer identity, certificate-backed digital signatures, formal notarization, or a controlled legal signing platform. Treat the output as a visibly marked PDF and always review the downloaded file before sending it to another person.

Step-by-step guide

1. Open the PDF SealBox tool and choose the PDF you want to mark.
2. Choose a preset stamp or upload a transparent PNG seal image.
3. Preview the page and click where the visible seal should appear.
4. Check that the seal does not cover names, dates, clauses, or signature lines.
5. Apply the stamp and download the stamped PDF for review.

Common mistakes

• Using a JPG seal image with a white background box.
• Placing the seal over a signature, date, amount, or contract clause.
• Exporting without checking the preview on pages with different layouts.
• Assuming a visible seal is the same as a certificate-backed digital signature.

Frequently asked questions

Key takeaways

• Use transparent PNG seal images when possible.
• Preview the placement before exporting.
• Avoid covering contract text or signature fields.
• Use certificate signing when legal identity validation is required.

Related guides