When users look for Office document to image conversions, they basically need one of two things possible. First thing is to simply get a picture of their document, which can be also done by print screen method or to export pictures saved inside the office documents (typically .doc, .ppt, .pps, .xls).
You may find utilities that can make both of these things, but both are also possible without any 3rd party software. As was said, making picture of your document is possible using PrintScrn button and then pasting the data to Paint program to crop and save it as image (commonly. .jpg, .jpeg, .png).
Specialized programs and converters of course make all this much easier and you will also get better results if you save your document as image in a program that offers this function, so you do not need to manually crop out the edges etc.
Articles and other information relating to doc into jpg conversion:
How to extract pictures from Microsoft Word documents - Exporting images from MS Word .doc and .docx files