i think there is a way to optimize images and word files for pdf.
another is splitting them. have you tried using winrar? i think that has better compression. if you have winrar, you can right click your file, then click add to archive, set the name, then at the lower left side, you can set best (for compression), and what size do you want it to be or usually the maximum limit of the email you are using.
have you tried uploading to online storage like mediashare.com, xdrive. com or skydrive.live.com? skydrive offers 5gb free, and i think there is a public folder, so you can share the link, instead of sending the file.
or try microsoft's beta mesh.com. go to mesh.com; connect your pc to the mesh by installing a small app. then go to the live desktop, create a folder, at the right side of the window (folder), there is the members tab, use it to add your friend's email. then go to your desktop, a blue folder should be there, just copy and paste your file inside this folder. and when your friend hook his pc to mesh.com, the your 5 page pdf will be automatically sync with your friend's folder in his/ her pc