Annotations are marks that you put on top of a document. With a tablet, you can take a picture of a document then put marks on it. That could mean text or handwriting in different colors. It could also mean highlights or notes.
SnapType Pro Best of Class Author’s Pick
With this app, you take a picture of a document and then type on a picture of the document. The fact that this app streamlines the process makes it an awesome app.
https://itunes.apple.com/us/app/snaptype-pro/id1124123246?mt=8
https://play.google.com/store/apps/details?id=com.snaptypeapp.android.pro
ClaroPDF
https://itunes.apple.com/us/app/claropdf/id666770153
PDF Expert by Readdle
https://itunes.apple.com/us/app/pdf-expert-6-read-annotate-edit-pdf-documents/id743974925?mt=8
Xodo PDF Reader & Editor
This app annotates PDFs and open Word documents.
https://play.google.com/store/apps/details?id=com.xodo.pdf.reader
https://itunes.apple.com/us/app/xodo-pdf-pro-highlight-sign-search-take-notes-edit/id805075929?mt=8
Annotations
This app allows you to label important notes with different colors. It helps you stay organized.
https://play.google.com/store/apps/details?id=com.mv.notas&hl=en