Open PDF and it is too small

So i open PDFs and then it is always too small.

So i click settings and options my only option is to type in my name.  That doesnt help. Where can i get to actual settings?

So i have to move cursor all the way down to the right to click that ADD button.

Then the pdf shifts left and when i scroll down it re-aligns and is centered. weird.

How do i set this up so that the initial pdf isnt small and i dont have to go down to that plus sign to make it bigger every single time.

I enlarged the size and then did a SAVE AS and when i went back in , it was again, too small and i had to enlarge again. I cant save in the size i want? why is this so limited??

There are also issues once in a while where stuff gets jumbled, but that is rare.  Why is there no settings option to set things up as you want them??