On the one hand, you mention an attachment, but then describe inserting data into the body of your email. Which do you want?
And how is the data you want to include in the body of the email set up in tables and relationships?
There are a number of calculations that you can use to pull plain text into the body of the Send Mail dialog from multiple records.
And a PDF can be saved and then attached to the email--but only one such attachment per email.
And there are plug ins that offer more email options than is possible with send mail...