Antenna House Regression Testing System (AHRTS) is an automated solution designed to perform visual regression testing of PDF output (PDF to PDF compare) from the Antenna House Formatter software by converting a set of baseline PDFs and a set of new PDFs to bitmaps, and then comparing the bitmaps pixel by pixel. Several functions of the system make use of XML and the final reports are generated using XML and XSL-FO. This paper addresses the importance of PDF to PDF comparison for regression testing and explains the visual comparison approach taken. We explain the issues of traditional methods such as manual regression testing and why the need for an automated solution. We also look at how AHRTS works and discuss the benefits we've seen since using it internally to test new releases of our own software. Given its visual-oriented capabilities, we then explore other possible uses beyond the original design intent.