I have been uploading photos that are 300 by 300 and scaling them down. It works for a while and then after a couple of days, the photos become blurry and pixelated. They also get the little red circles with the question marks inside. I have changed the view to high res and all of that but it doesn't seem to help.
Can anyone help?
When you use the File > Place command and select a picture, you're linking to an external file. The pictures are not embedded in the InDesign file.
The circles with question marks means that the program has lost track of the location to the original files. You use the Links panel (Window > Links) and the Relink button (or choose Relink... on the panel menu) to relink the external pictures.