PITT 6.1.3 could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The PITT installer is commonly called PITT v6.1.3.exe or PITT v6.1.exe etc.
We recommend checking the downloaded files with any free antivirus. The most popular versions of the program are 6.1 and 1.2. The actual developer of the free program is Cygnacom Solutions. PITT lies within Development Tools, more precisely Debugging Tools.
From the developer:
The PKI Interoperability Test Tool (PITT) is a utility intended for PKI integrators. It allows inspection and troubleshooting of certification path processing for a given PKI using both PKIF and Microsoft CAPI.
You may want to check out more software, such as ClearView or Froggy Castle 2, which might be similar to PITT.