This is most probably a very "rookie" question, however my opinion is that it's better to ask than to stay ignorant even if the question is very elementary.
When importing images into your Scribus document like for example digital photo's or scans you usually resize them within Scribus to suit the lay-out of your page. When simply resizing the image the source file keeps its properties, yet that will make the document size (unnecessarily) big.
Example:
When importing a digital photo with an original file size of 5.4 Mb (resolution 450 DPI) and resizing it to frame of 200 pixels wide by 364 pixels high, the size of the photo remains the 5.4 Mb it originally is for the Scribus document. In order to keep your document size manageable you would want the file size to more or less correlate to the image size used in the document without touching the original resolution to keep quality during printing high.
How do you tackle this issue? Rescaling the original digital photo to the size you want in your Scribus document is of course an option, but if you later want to enlarge the size again in your document you will get quality loss, since you modified the size of your original photo.
Thanks in advance for any reply, Ronald