Explain the problem as you see it
Tana's PDF viewer does not remember the page that it was last opened to.
Why is this a problem for you?
I lose the page I am reading as soon as I navigate to another page/node, or if I return to the reading later.
This has required me to look for and write down the page number before closing, which is not ideal.
Suggest a solution
Do what logseq does; remember the page location/number whenever you navigate away - making it easy to return to what you were doing at another time.