How to add an invoice approval stamp and signature to a PDF
Accounts-payable teams use stamps to enforce internal controls — a PAID, APPROVED or coding stamp shows an invoice has cleared review before payment. But if a “PAID” stamp is just a pasted image anyone can copy, internal invoice fraud spikes. With PDF Verified you can add an approval stamp and an authorising signature to an invoice PDF online, and serialize each stamp with a public QR verification link so approvals are provable, not fakeable. No printing, no scanning, and it fits straight into an AP workflow.
How to add an invoice approval stamp and signature to a PDF — step by step
- Build your approval stamp — Create a PAID, APPROVED, RECEIVED or a custom coding stamp (with GL code, cost centre or approver fields). Turn on serialization with a prefix like AP- so each application gets a unique number.
- Stamp and sign the invoice — Upload the invoice PDF, place the approval stamp, add the authoriser’s signature and the date, and mark it approved for payment.
- Download the verifiable record — Download the stamped, signed invoice sealed with a SHA-256 fingerprint and a QR verification link, so finance and auditors can confirm the approval is genuine and unaltered.
What you get
- PAID, APPROVED, RECEIVED and custom coding stamps with approver/GL fields.
- Serial numbers + public QR verification so a copied “PAID” image can’t pass.
- Authorising signature and date captured on the same PDF.
- Tamper-evident SHA-256 seal and audit trail for clean approval records.
- Paperless — fits an accounts-payable workflow with no printing or scanning.
Frequently asked questions
How do I add an approval stamp to an invoice PDF?
Create a PAID or APPROVED stamp in the PDF Verified stamp maker, upload the invoice, place the stamp and the authoriser’s signature, and download the stamped PDF. Turn on serialization so each approval carries a unique, verifiable number.
How do I digitally sign an invoice?
Open the invoice in PDF Verified, add the authoriser’s signature (draw, type or upload), place the approval stamp and date, and download the sealed PDF. The signature is bound to the document by a SHA-256 hash, so it can’t be lifted onto another invoice.
How does this prevent invoice fraud?
A pasted “PAID” image can be copied onto any document. A PDF Verified approval stamp is serialized and resolves to a public verification page showing the serial, the invoice it was applied to and whether it was revoked — so a faked or reused approval fails the check.
Can I add GL codes or cost centres to the stamp?
Yes. Build a coding stamp with fields for GL code, cost centre, approver initials and date so AP coding and approval happen in one mark.
Can I stamp invoices in bulk?
You can create a reusable approval stamp and apply it across invoices; on Business plans the shared stamp library and serialization keep every approval consistent and auditable.
Is a stamped, signed invoice legally valid?
The signature makes the approval legally binding under ESIGN, UETA and eIDAS, and the stamp plus SHA-256 seal and audit trail give you a defensible record of who approved what, and when.