Any thoughts why Adobe Acrobat's Action Wizard makes file-sizes larger?

[Todd's keyboard]

Am preparing some pdf's to put on web pages. Using Acrobat X Version 10.1.16 "Action Wizard" to "Prepare for Web Publishing."

The original document is 7.4 MB. The "Prepared" document is 10.1 MB. This is using the default options that Acrobat presents.

Any thoughts as to why? Strategies to lower the file size?

thanks, Todd's bloated keyboard