PDF files are used everywhere and can be used on Chromebooks. Here are some resources:

Adobe Android apps work very well on Chromebooks and there are other Android apps for working with PDF files:
https://drive.google.com/open?id=1gyZbgMwMbLBuPYb3NybSHnVus3jKsA81

– Xodo PDF Reader and Editor https://play.google.com/store/apps/details?id=com.xodo.pdf.reader&hl=en_US

– PDF Editor – https://play.google.com/store/apps/details?id=com.kmo.pdf.editor

– PDF Editor – Sign, Create, Edit https://play.google.com/store/apps/details?id=com.offiwiz.pdf.editor.reader

– Write on PDF (annotate, not edit) https://play.google.com/store/apps/details?id=com.samsung.android.spdfnote

Managing Android apps on Chromebooks: https://support.google.com/chrome/a/answer/7131624

Android on Chromebooks! Here are some resources and apps to check out http://educationaltechnologyguy.blogspot.com/2017/02/android-on-chromebooks-here-are-some.html

Different ideas: