For most uses this setting works well to flatten files that have image quality issues like:

• transparency issues
• layering issues

Notes

• For higher quality you can convert the file to 1200dpi. However, higher dpi will cause longer load times which can delay a project. If the file is too large it also may crash our systems.
• We set the color mode to RGB because it keeps the correct scaling when converting back to PDF.
• Anti Aliasing should be checked to keep the images looking sharp. 
• After creating the jpg file it's critical to check the quality against the source file to make sure the file looks good.