Adding a digital signature to a PDF using Java

I want to digitally sign a PDF file using a certificate stored on a USB-token, HSM, etc. How do I use the private key stored on the USB token using JAVA?

Can I add a digital signature to a PDF?

Open the PDF document or form that you want to sign. Click the Sign icon in the toolbar. Alternatively, you can choose Tools > Fill & Sign or choose Fill & Sign from the right pane. The Fill & Sign tool is displayed.

How do I add a verified digital signature to a PDF?

Open the Preferences dialog box. Under Categories, select Signatures. For Verification, click More. To automatically validate all signatures in a PDF when you open the document, select Verify Signatures When The Document Is Opened.

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