Patrick,
Assuming you embedded your picture, first select your picture, go to Format
Scale Picture (or right click the picture > Change Picture > Scale
Picture) and confirm that it is at the original or 100% size.
If that doesn't help, then perhaps work on the images prior to inserting
them. Using your favorite image editing software, reduce the size of the
image to the same size as you intend to use in your web document, and
'optimize' it for the web. How you do this will vary with the image editing
software. The trick, which is through trial and error, is to not over do the
optimizing. Reduce the size just to that point that it still looks good when
you preview your Pub doc.
HTH and have a happy Thanksgiving.
DavidF