If you don't have access to a large format printer or if you just need to print a large PDF right away, there is an option in Acrobat Reader to print a large file onto multiple regular sheets of paper.
About halfway down the screen after you hit print, on the options screen, there is a section called Page Sizing and Handling. Under that label there are four buttons labeled Size, Poster, Multiple, and Booklet. By default, the Size button is selected which gives you options to scale the image to fit the paper, print it full size (which will cause only the middle part of the image to print), or set a custom size.
Ignore all of these options and hit the button labeled Poster. You'll then have options for tile scaling, overlap size, and a few other things. Just make sure that tile scaling is at 100% and the preview window will show you how it is going to print out. For the 42"x30" PDF it will end up printing either 5 sheets wide by 3 sheets tall for a total of 15 sheets or 4 sheets tall by 4 sheets wide for a total of 16 sheets depending on if it wants to print it in portrait or landscape orientation. I'm sure you could tweak the settings to make it print however you want but this will get you a properly sized printout.
Hopefully this will help somebody out and maybe save you some time and/or money.
