Yes. The ability to optimize a photo was introduced in version 5 and can be accessed by right clicking on an image and selecting the optimize photo option.
Version 6 has simplified the Photo Optimize dialog and introduced an Optimize All JPEGs.
Utilities -> Optimize all JPEGs is a quick way to reduce the file size of documents containing many JPEG photos.
When you import a photo (either using the Import menu or by drag n drop from File Explorer) the program can embed the original, full resolution JPEG. This still saves a huge amount of memory and file space compared to other graphics programs that typically convert the JPEG into a raw format. If you open the bitmap gallery, you will see that the original image is saved within the file. (only 1 instance of the original image is saved within the file, all instances used within the document are generated on the fly.)
As an example, embedding 10 photo from a typical modern digital camera might easily take 50Mbytes (5Mbytes each) so your xar file would be 50Mbytes + a small amount for text and shapes used within the document. In addition to this, the images taken from a digital camera are likely to be are far higher resolution than needed for either print or screen or web work. Optimizing would not only reduce the resolution but also the file size for each JPEG.
This results in a smaller file size and less memory usage on export.
We recommend applying the optimize all function prior to export for those exporting websites or creating documents consisting of many JPEGs. Please see the following article for more information