Pkcs11Admin is described as 'open-source GUI tool for administration of PKCS#11 enabled devices (smartcards, HSMs etc.) which runs under .NET 4.5 on MS Windows and under Mono 3.X on Linux and Mac OS X'. There are more than 10 alternatives to Pkcs11Admin for a variety of platforms, including Windows, Linux, Mac, Self-Hosted solutions and Online / Web-based. The best alternative is xca - X Certificate and Key management, which is both free and Open Source. Other great apps like Pkcs11Admin are YubiKey PIV Manager (Free, Open Source), VeriSign (Paid), EJBCA (Freemium, Open Source) and OpenXPKI (Free, Open Source).
X Certificate and Key management is an interface for managing asymetric keys like RSA or DSA. It is intended as a small CA for creation and signing certificates. It uses the OpenSSL library for the cryptographic operations.
OpenSC provides a set of libraries and utilities to work with smart cards. Mainly on cards that support cryptographic operations, and facilitate their use in security applications such as authentication, mail encryption and digital signatures.
PKI solution based on Microsoft AD CS (Active Directory Certificate Services) offers a affordable and powerful digital certificates environment, however sometimes it can be challenging to use without additional tools (3rd party utilities or scripts).