JSignPdf
Add digital signatures to PDF documents - GUI and CLI, cross-platform
...Supported capabilities include PKCS#12 keystores, smartcards and hardware tokens (PKCS#11), Windows keystore integration, visible signatures with custom images and positioning, timestamp authority (TSA) support, OCSP/CRL revocation checks, certification signatures, and PDF encryption.
Cross-platform (Windows, Linux, macOS), built on the OpenPDF library, and translated into many languages by its community, JSignPdf is a trusted choice for anyone who needs reliable PDF signing without commercial licensing.