Do you mean displaying these files on a html page, but not allowing people to save them?
If so, then I don't know of any techniques to keep pdfs from being downloaded. For images, the only way to do this through CSS by declaring a background image for an html tag. Use the css style attribute and background property. Here's an example with a div tag, assuming an image's dimensions are 100x100:
Code:
<div style="background:url(pathtoyourimage);width:100px;height:100px;"></div>
Where pathtoyourimage is the path and file name of the image.
You can use this technique for most html tags, including anchors and headings.
But if people really want the image, there is no way to stop them from taking a screen shot.