Something to play with -
Go into Acrobat's Preferences. Select the Convert to PDF category.
Pick as desired from the list of support applications / file formats.
Some have an active "edit" button. If so, click it then configure.
See if changes there (i.e., to JPEG or TIFF) make a difference.
Message was edited by: CtDave
Since I don't know what exactly to change in preferences, I've made some changes which did not make any effect.
With the highest quality exporting, the pictures in the document still look awful. And I need to deliver the document today... so too little time left to solve this problem.