Assalamu Alaykum Ustadh, is it fine to study knowledge using PDFs rather than having the physical book itself. And if so, can you please recommend how to take notes online if you have experience in this e.g. any useful apps? I find this to be cheaper and easier to study.

Ustadh AbdulAziz al-Haqqan

I use this all the time and I have a samsung table s10 plus and use the app samsung notes, it is extremely useful as it syncs with my phone as well.