SharePoint & MarkUp on iPad Pro

Hello

I use SharePoint regulratly for my files and when I pull a PDF from SharePoint there is no way for me to markup my PDF using the Apple Pen, at this point I am having to email the document to myself, download and then I can get the markup option to work. Any suggestions on how to get the markup function to work properly directly out of SharePoint, this process is quite cumbersome and I am second guessing my iPad Pro purchase