Eraser tool in pdf reader with freehand draw and normal touch selective for scrolling using s-pen

hi everyone,

I Use adobe pdf reader for reading on my samsung tablet, it is a really good app and quite user friendly.  I use free hand writing tool mostly for under line and highlight as well as notes taking to keep tool change to minimum, issue is when I have to scroll it draws random line on the page.

Firstly there is no eraser tool so only option is to undo it that creates issue when I find out that there is a random line sometime later and I can't undo all the annotations.

Second there must be option where S-pen can be used to draw and finger or normal touch can be used to scroll the document.

Thanks