Spamming is the word commonly used to describe Net abuse via e-mail or newsgroups. Spammers get your e-mail address in many ways. There are companies that collect and sell e-mail addresses. They acquire your e-mail like they do your phone number or mailing address. The difference between this and junk postal mail is the fake source.
Spammers hide themselves and use many fake addresses for each occasion.
There are e-mail filters which block addresses and domains but addresses are easily faked and one can't afford blocking domains completely. Remember not to read suspicious messages. There is a lot of help out there. Of course, if the document contains images or links that are on different pages, you'll lose these. Make sure you browse all the available programs before downloading one.