A. You can change the sheet size in page setup. Then you have to move the contents of the LO file to center on the smaller page as you want (do this with a copy of the LO file). I tested printing to pdf. Of course if you have a large solid SU window or object it will cover the smaller page on screen, but it's doable by making a rectangle to represent the page and checking under "Pages" window.
B. LO changes the printable area by the page setup window so there is no direct "reduce to fit option". What's not on the white space won't print, on Mac anyway. You can print to pdf full size then print to a smaller sheet in "Preview" or "Acrobat". In other programs I would find that I could adjust the percent scale in Page Setup and the smaller page would encompass more of the image. Adjusting the scale in page setup doesn't seem to do anything in LO.
