How To Annotate PDF Online?
Upload & Edit Your PDF Document
Save, Download, Print, and Share
Sign & Make It Legally Binding
Easy-to-use PDF software
What are some (preferably Android-based) devices for PDF reading and annotating around $150 for a PhD student who needs to read academic papers and also take notes?
I would go for a tablet with a high resolution screen and decent screen size. A MS Surface Pro/Book would work. Whatever you get needs a proper keyboard to make notes and preferably a stylus to draw on the document. For that reason I would avoid an iPad which has a really crappy on screen keyboard.
Annotate PDF: All You Need to Know
I also think that a full sized tablet with a keyboard/mouse is better because the pen becomes unnecessary. If you get a tablet at school or work that is not an option, and you just want access to your files while on the go than an iPhone or iPhone mini are great options.