That's what mailmerge is for. Both Outlook and Word have tools for that. On the Word front, you might be interested in the Many-to-One Mail Merge add-in from Doug Robbins at
http://bit.ly/1hduSCB
In addition to a 'Many to One' merge, the addin handles:
• Merge with Charts
• Duplex Merge
• Merge with FormFields
• Merge with Attachments
• Merge to Individual Documents
• Merge, Print and Staple