Some Word 2007 documents that contain images produce very large PDF files with Win2PDF.

 

Solution:
Word 2007 has an option to reduce the resolution of images in the document which dramatically decreases the PDF file size. To reduce the file size, click on the "Format" ribbon and choose the "Compress Pictures" option at the upper left corner of the ribbon toolbar. Choose "All pictures in document", "Web/Screen", and enable the "Compress pictures" and "Delete cropped areas of pictures" options. After clicking OK and printing to the Win2PDF printer, the PDF file size will be dramatically smaller.

These options are described in more detail at:
https://support.microsoft.com/en-us/help/2002066/loss-of-image-quality-after-you-save-in-word-excel-or-powerpoint-2007