There are a wide variety of tools on the market for document preparation, ranging from familiar WYSIWYG word processors to esoteric systems designed for publishing houses. Today we are in the position where documents usually need to be published both electronically and on paper. The preferred electronic standard is PDF (Portable Document Format) which incorporates in-built compression to minimise bandwidth demands.
Probably the two most commonly employed tools for document preparation are Microsoft Word and LaTeX. To cut a long story short, LaTeX is better! Whilst it has a slightly higher initial learning curve, this easily pays off in the long term. It produces superior documents with correct formatting of mathematics and text, has never crashed on me, has an excellent in-built system for referencing and can directly produce PDF documents for electronic distribution and printing. If you are still not convinced take a look around at the people who write the most papers and see what their preference is. What's more LaTeX is free and available for virtually all computing platforms.
Here is an example of a PDF document produced with LaTeX. I would show you the inferior document produced by Microsoft Word, but I received the message "Microsoft Word has encountered a problem and needs to close".