We have some very complex process line drawings done with Pages (Word can do it too). You don't need any fancy software programs for basic process drawings, just a desire to learn how to manipulate programs like Pages (Apple) or Word (Microsoft), and some patience.
The attached image is a very complex line drawing all done on Pages. It took seven evenings to complete.
I am happy to get you started and forward a basic design so you can continue updating with your own changes.
My preferred word processing program is .docx (Pages - Apple), but are happy to forward it in .doc (Word) too.
Go to our mySerenity Website for more great ideas.