Fundamentally, there is nothing you can do. The way a browser works is it
downloads all the binary files from a site along with the text and displays
them onscreen. By necessity, in order to view a page your must download the
page's contents, images and all, to a local memory cache and accessing it
for "archiving" that info is relatively easy.
Your best bet is to watermark the dickens out of your materials. Or like
someone else suggested, don't post them online!