How do I tell acrobat to remember the window size? I am running Acrobat Pro version 2021.001.20149. Mac High Sierra. Example: open pdf. Resize window. close pdf. open pdf. I have to resize window again.
Normally Adobe Acrobat remembers the last viewed state of a document if you've enabled "Restore last view settings when opening documents".
This preference setting is accessed via clicking on "Edit" --->>> "Preferences" --->>> "Documents".
Just rememeber, this is a global preferences settings.
NOTE: If you're asking how to make a specific Page View to stick with a specific document everytime it is opened, then try this:
Open the document in Acrobat
Click on "File"--->>> "Properties"
Then go to the "Initial View" tab. There are three subsections, but two of interest to your case. These are: "Layout and Magnification" and "Windows Options"
See if this resolves your issue.
If this is not what you're inquiring, then you may also want to explore with the Print Production tool --->>> "PDF Fixups", by which you can customize a specific page scale profile just for that particular document.