Is it picking a file by name or do you want to open a specific folderr and browser for the file?
For the first, you use attachment.add:
Code:
Set oMail = objApp.ActiveInspector.CurrentItem
With oMail
.To = oContact.Email1Address
.Subject = Left(oDoc.Name, Len(oDoc.Name) - 5)
'The content of the document is used as the body for the email
.Body = oDoc.Content
.Attachments.Add "c:\path to \Documents\instructions.pdf"
.Display ' .send
End With