Question

How to remove the signature, text, stamp, logo or other color marks from the document?

Answer

If the signature, text, stamp or logo is in a different color, you may use the "Remove all color marks" option in Project Properties in Image Processing settings:

This option is also present in Batch Type Properties and Image Import Profiles, depending on your project settings.
 
It's also worth mentioning that you may use custom Image Enhancement Profiles to fine-tune color removal and other image enhancement options.
You can create your custom Image Enhancement Profile in FlexiCapture:
1. Open your FlexiCapture project in Project Setup Station;
2. Open Project Properties and go to Image Enhancement Profiles tab;
3. Click on "New", enter the name, load preview, and tick "Remove Color Marks", you may also select the particular color to remove:

After that, select it to use for Image Processing:

This option is also present in Batch Type Properties and Image Import Profiles, depending on your project settings.

For additional information check wiki: Image Enhancement Profiles