The standard document converters that ship with Alfresco uses OpenOffice (or LibreOffice) for conversion of some documents to PDF. When it comes to converting Microsoft Office documents to PDF or PDF/A, with OpenOffice the end result is sometimes not as good as the original. This is especially true for conversion of the newer XML based formats (like .docx, .xlsx, pptx etc). Callas pdfaPilot is a product that does this by using native Microsoft Office for the conversion process and also by using it's own advanced PDF/A technology for creating valid PDF and PDF/A documents.
This extension to Alfresco is implemented as a subsystem in Alfresco and can easily be switched on and off (preferably with the JMX control mechanism, available through VisualVM). It uses the satellite and dispatcher setup that pdfaPilot has, and can therefore be run against a remote Windows server (if native Microsoft Office conversion is needed) from an Alfresco server which has the pdfaPilot CLI client.