Assembly Error During Runtime

I have a C# application that I built to generate reports and export them to PDF. It runs fine on my machine (when debugging and when compiled to an .exe). When I try to run it on other machines, I get an error:

Could not load file or assembly 'CrystalDecisions.CrystalReports.Engine, Version=10.5.3700.0

I thought the assembly would be included with the .exe file when it is compiled, but apparently it is not.

Am I doing something wrong or is there something I have to do to get this to work successfully?

Thanks

Dan