Does the PDF need to remain a PDF? Another even better solution for inking is to print the PDF to OneNote.
I did this for the first time today - I printed a journal article to One Note at work, then when I was out for lunch I sync'd my surface to it (Surface is my own personal device and I can't use work network so had to be out and about and on a public wifi - how mad is that!) then I used the pen and annotated the OneNote version in the MUI version of OneNote.... it was fantastic. This is a game changer for me - I should now be able to remember where I put journal articles and actually be able to go back to them - they'll all be in One Note!