When starting a drawing, am I stuck with what ever the initial page/drawing size are set to, or can I take the same file and print it out at both 7x11 and 24x36? Also is preserving visio layers at all possible when printing to PDF or converting natively?
http://www.visguy.com/2016/12/29/visio-circle-arrows-2013/
You can change the paper size from the Page Setup dialog. Choose whatever size paper you want.
The Print zoom can also be changed.
I don't think PDF files understand layers. However, you can print any combination of layers to a PDF file, just set the layers you want to printing or non-printing.