can i speed up my Imac ?

Hi,

My iMac that I purchased in 2009 is getting very slow, particularly in sending printing jobs, Is there a way to increase its speed? either by changing the processor or add a processor externally?

Here are my specs:

Model Name: iMac

Model Identifier: iMac9,1

Processor Name: Intel Core 2 Duo

Processor Speed: 2.66 GHz

Number of Processors: 1

Total Number of Cores: 2

L2 Cache: 6 MB

Memory: 4 GB

Bus Speed: 1.07 GHz

Boot ROM Version: IM91.008D.B08

SMC Version (system): 1.44f0