It sounds like a mail merge of a single selected record - see
Mailmerge with Word 2007/2013 .
You may also do it using VBA to look up the record, and for single records that is probably the most elegant way forward, though without more information about the worksheet, it is difficult to be specific?
Take a look at
http://www.gmayor.com/Userform.htm and
http://www.gmayor.com/Userform_ComboBox.html