Here is what I did to rip pictures from a PDF. I used a tool called LibreOffice, which allows you to edit PDF files, if you don't have the full version of Adobe Acrobat. This gives you the ability to pull maps from the PDF and removed all of the labels that would spoil the immersion for players. To grab the individual picture in full resolution you can use a PDF splitting tool to get yourself a PDF of the single page from the full PDF file. A quick google search like "Splitting a page from a PDF" will tell you how. From there you take the page into LibreOffice to grab the image without the text overlays from the PDF. Then you just save the page as an image with LibreOffice, I did this on accident so you might have a bit of trial/error to get it. Im sure there is a help entry or something on LibreOffice but I dont know for sure. It split up all the elements of the page and it looked a bit derpy on my screen but I right clicked it and pressed "View as image" or something like that. From there you open it with your favorite image editor and crop the part of the page you want and then save it. Then find the file in your file browser and click and drag it onto Roll20. Bam, PDF to Roll20 in a bunch of steps which I am sure someone else could do easier! Haha, this is how I pulled maps from Legacy of Fire into Roll20 to use as player maps. Hope I could help you, and good luck! Also dont worry about libre office, I think its pretty legit. I tried a few others but this was the only one that actually allowed me to pull the background image without the text elements. Godspeed, good sir.