If you drag a PDF to the Win2PDF Desktop icon, or select a PDF from the open window when launching the Win2PDF Desktop application, the following options will be displayed under the "File" menu:

 

 

After selecting "Export -> PDF - Compressed", you will be prompted to save compressed PDF file.  After saving the file, you will be given a summary of the compression results:

 

 

The compression savings will vary depending on the document, but files with color images will benefit the most from compression.