Mr. Hunt,
You will discover that different email providers cap email (and related attachments) at different sizes.
Since you have a document that is a PDF, then there are a few tricks to reducing files sizes. However, there are a few limitations.
The first is to use a copy of Adobe Acrobat (authoring software, not the freebie "Adobe Reader"). Acrobat will let you create additional copies with pages removed. Example...take "The First.PDF" and make a copy called "The First Half.PDF." Then, edit the new file to delete/remove all pages after the first half and save the new document. Now, again take "The First.PDF" and make a copy "The Second Half.PDF" and edit to remove/delete all the pages from the first half and save this third document. Now you should have the original, large "First.PDF," a reduced-in-size "The First Half.PDF," and a reduced-in-size "The Second Half.PDF."
Now send two emails, one with the first half, and one with the second half.
Doing this just chunks up the original file into smaller sections with no loss of quality, but it will require sending those chunks via more individual emails.
The second solution from a high level view, is to learn how to reduce the file quality. From Adobe Acrobat again, re-save the file In a lower quality setting. I don't like this answer specifically because of the quality reduction.
The third one requires a copy of Windows that allows for compressing folders. So this means place the file in a compressed folder...in short, Windows just created a .ZIP file that may be small enough to make it through most email services. Other utilities may be installed/employed to do the same thing on just the PDF. WinZip and 7-zip are a couple that come to mind-no financial interest or endorsement. As in option one, this one does not require file degradation to reduce the file size...caveat-the file may not reduce enough.
I hope this helps...