FAQs
How to add a digital signature to a PDF in Adobe Acrobat Reader DC (USB token).
Overview
By following this article, you will apply a valid digital signature to a Portable Document Format (PDF) file so that recipients can confirm who signed it and that the content has not changed. The procedure uses Adobe Acrobat Reader DC and a document signing certificate held on a Universal Serial Bus (USB) hardware token. It is organized in two stages: first you select your certificate as the signing identity (ID) in Adobe Reader, then you place and apply the signature on the document. If enabled, a timestamp from the Sectigo timestamp server is added at signing.
Note: The steps below were captured in Adobe Acrobat Reader DC version 2025.001.20844. Screens may differ slightly in other versions of Adobe Reader or Adobe Acrobat.
Similar questions
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How do I sign a PDF with a certificate in Adobe Acrobat Reader DC?
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What are the steps to add a digital signature in Adobe Reader?
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How do I select my document signing certificate in Adobe Reader?
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Can I use a USB token to digitally sign a PDF in Adobe Reader?
Prerequisites
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A document signing certificate installed on a USB token.
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Adobe Acrobat Reader DC installed on your computer.
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The token client software (for example, the SafeNet Authentication Client) installed and running.
Step 1 - Select your certificate in Adobe Reader
This stage sets your document signing certificate as the identity that Adobe Reader will use to sign. Complete it once before you sign a document.
1. Insert your token into a USB port on your computer.
2. Open the PDF document in Adobe Reader.
3. From the Menu, click Preferences.
Figure 1: Adobe Reader Menu open with Preferences selected to begin certificate setup.
4. On the Preferences page, select Signatures.
5. Under Identities & Trusted Certificates, click More.
Figure 2: Preferences page on Signatures, with More under Identities & Trusted Certificates highlighted.
6. On the Digital ID and Trusted Certificate Settings page, select Windows Digital IDs and choose your document signing certificate from the list.
7. From the pencil (edit) menu, select Use for Signing.
Figure 3: Digital ID settings with Use for Signing selected for the chosen certificate; account names and identifiers are redacted.
8. Close the Digital ID and Trusted Certificate Settings page, then click OK on the Preferences page.
Step 2 - Sign the PDF document
This stage places the signature on the page and writes the signed file. Make sure you completed Step 1 first.
1. Ensure your token is plugged into a USB port on your computer.
2. In Adobe Reader, select All Tools, then View More.
Figure 4: Adobe Reader All Tools panel with Use a certificate highlighted.
3. Scroll down, click Use a certificate, then select Digitally Sign.
Figure 5: Use a certificate panel with Digitally Sign selected.
4. Read the information dialog and click OK.
Figure 6: Information dialog explaining how to draw the signature area.
5. In the PDF, click and drag to create a signature field.
6. Confirm the correct certificate is selected and click Continue.
Figure 7: Sign with a Digital ID dialog for choosing the signing certificate before continuing.
7. In the Sign Document dialog, adjust the signature appearance if needed.
Figure 8: Sign Document dialog showing the signature appearance and date before signing.
8. Click Sign. When prompted, choose a file name and location for the signed PDF, then click Save.
Figure 9: Save As dialog for naming and saving the signed PDF.
9. When asked, enter your token password so Reader can use the certificate.
Figure 10: SafeNet Authentication Client token logon prompt for the token password.
10. If prompted to connect to the Sectigo timestamp server, click Yes.
How to verify the signature was applied
The signature appears in the area you selected, showing the certificate details and the signing date. Adobe also displays a banner at the top of the document confirming the PDF is signed.
Figure 11: Signed PDF showing the applied signature with date in the selected area.
Troubleshooting
Issue: Your certificate does not appear in the signing list.
Cause: The token is not connected, or its client software is not running.
Solution: Reinsert the token, confirm the SafeNet Authentication Client is running, then reopen the dialog.
Issue: Adobe Reader does not prompt for a timestamp.
Cause: Document timestamping is not enabled in Adobe Reader.
Solution: Enable Document Timestamping under Preferences, Signatures, before signing.
Frequently asked questions
Do I need a hardware token to sign a PDF in Adobe Reader? This procedure uses a hardware token because the document signing certificate is stored on it. If your certificate is in the Windows certificate store instead, select it under Windows Digital IDs the same way.
Can I add more than one signature to a PDF? Yes. You can add one or more digital signatures to a PDF file or form. Repeat the signing stage for each signature field.
Why is a timestamp added when I sign? A timestamp from the Sectigo timestamp server records the exact time of signing, which helps prove the signature was valid at that moment.
What is the difference between Adobe Acrobat and Adobe Acrobat Reader for signing? Both can add digital signatures using this procedure. This article uses Adobe Acrobat Reader DC.
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