Can I legally use an alias to do moonlighting drafting work in PA??

I do computer aided drafting (CAD). I am currently full-time employed with an engineering company. I would like to make some money 'on the side" by marketing my CAD services to some smaller companies. Now I know that moonlighting is a conflict of interest with my current company, and I'm ok with that. I will be marketing to much smaller clients than my current emplyer would ever seek or even contract with. So, I am ok with the "conflict of interest" with my current employer and am aware that is something that I will need to deal with if I am discovered. SO, to help hide my personal identity when sending out marketing pieces, and writing letters, I was thinking aobut using an alias. Is that legal? It may be a little morality issue that I would need to get over, but how about the legalities of the issue? I would do the work under a company that I will form, but can I use an alias, or even an abbreviation of my name, such as just my first and middle name? Should I register my alias some how with the state, like a "fictcious name" as a company would? Besides the morales, and the conflict of interest with my company, is is legal to use an alias to conduct business in PA? and if so, can I make it legal? I should mention, that I will not be meeting people in person. All "alias communicaiton" would be by way of phone, email, letters, reports, drawings, etc.