Printing - You can usually print these in half size without any problem, since the originals were about that size anyway.
     When printing from Adobe, under "Page Sizing & Handling" click "Size," then select "Fit." (Older Adobe says "Fit to Printable Area.") Then the image fills the page. Of course, this might vary from one book to another, so see what looks best before printing. (Wording can vary in different versions of Adobe, and will be different in other PDF readers, but these directions should still lead you in the right direction.)
Text option - Uncorrected OCR text is usually available as well as the PDFs or scans. (See below)
Scan Color - Most online scans (like at Google Books [GB], MOA, Canadiana, etc.) are crisp black and white. But sometimes the older PDF scans at the Internet Archive [IA] are yellowed, and may print a gray background, but 1) IA is offering many more books in BW, even if also scanned in color, and 2) if not, there is a way around it.

Quick-Fix for Yellow Scans - (Note: This method worked with older versions of Adobe, but as new versions are released, I can't guarantee the same method will work.)
     Once the PDF from IA file is downloaded and opened in Adobe, look at the row of tabs at the far left. Click the one that says "layers". Click on the picture of the eye next to where it says "Background" and it will get rid of the colored background for you. The text and b & w pictures come out quite well. Colored pictures need the background turned back on, but most books have b & w pictures anyway.
     [I did a book with colored pics as follows: I printed different sections of the book at a time (pages without pictures) to FinePrint, so all the text pages ran together. (It combines all of the jobs for you.) After printing those I turned the background back on and printed the pictures on toner saver in b & w, then inserted into the book. (Many old books have a blank page after the picture page, and often they are without numbers, so it works out perfectly.)]