Sometimes you can get away with printing the web page to a PDF (choose that option in the print dialog box). The results are often optimised for the printed page, but might be useful in some circumstances.
yup, I also tried Grab, it fails to do this trick, other options like Webpage Screenshot Capture, Capturefullpage, CTRLQ, Snapito and many more can screenshot the entire webpage and save as image file. They are all web-based tools and totally free of charge. You can try it yourself or search more solutions on the web.