Still having issues

[handrawn]

if you post up a PDF that you scanned, we can check it and see if it lags when we ink in xara, you say you have xara 10 - is that xara designer pro 10 or xara photo and graphic designer 10

I will try it myself on a scanned PDF that I scanned myself and xara designer 10, but it would be a better test if you posted one of yours - PDF is a file container format and they are not all created the same way

inking is a process - you can use any image at all and ink on top of it for the purposes of testing - one downloaded from the internet for example, one you drew in your painter prgram

nvidia is only one option, the only sure way to know what your computer actually needs is if you tell us the make and model and then we can look it up - it's not likely, just worth checking

Paint 3D is not going to be a problem in itself