based on vendor web site: PD4ML Cookbook - HTML-to-PDF converter for Java and .NET the svg support starts from 3.8.5. I know the later version of pega (7.1.x) uses at least 3.9.0 of pd4ml. So SVG should be supported. You may want to browser the vendor web site to hopefully find the answers of your questions.
I just tested this on a PRPC719 system: it works ! But you will need to ensure you set the HTMLTOPDF parameter "pyHTMLDisableProcessing" to 'true' - otherwise the 'HTML Tidy' mechanism will strip out the SVG tags from your input document !
I used a slightly modified version of the example input on the page that Kevin Posted - resultant PDF is attached.
Simple HTMLTOPDF wrapper (note I am using 'Pass current parameter page' for each call here).