When converting files to PDF, is there a way to get rid of very dark background colors ?

I am using Windows 10 and Acrobat Pro XI.  I am downloading more and more manuals, and other files from the internet that have almost a solid black or other real dark color in the background and inside many areas of the  sections on the pdf's.  To print it out would waste so much ink and make the page limp. Is there a way to get rid of the dark colors?  I can barely use Acrobat Pro XI, so please break you answer down to baby steps.  A lot of times, I am told to do or make something that I have no idea even where to find what you are talking about.  I have used the program for years, and still struggle like crazy with it.  I don't know what a fourth of the menu items mean or how to make them work.  They are also making more and more instruction pdf files on the internet that are way to small to fit to a letter-size piece of  paper.  You can't even read them, they are so small.  I would greatly appreciate help with this.  I just noticed you could attach a file.  I attached one page out of the manual I converted to a pdf so you could see the colors.  Each page is also a weird size to try to print.