Why does my file increase when I convert to pdf?

Are you on Windows or Mac?  How are you creating the PDF from Word?

If you are on Windows, and use the Acrobat Ribbon.

1. Click Preferences before you click Create PDF
2. The Settings tab gives you access to the PDF Maker Settings.
3. Change the Conversion Settings to Smallest Files Size and see it it makes a difference.

You can verify where the extra megabytes in the PDF you created comes  as well as try and reduce it using Acrobat.

1. Click Tools
2. in the 'Find your tool here' search box type 'Optimize'. You should see 'Optimize PDF' as a tools option, with 'Advanced Optimization' listed. Click on Advanced Optimization.
   
3. You'll prompted to save the document (use a different name so you don't overwrite the original PDF you created).
4. Click Audit space usage.
   
5. Based on the information in the Audit Space Usage dialog box you can then use the PDF Optimizer to reduce the file size in those areas. E.g. for Document Overhead, try selecting 'Discard Objects' and 'Discard User Data'. For images, select Images and adjust the Image settings.