One way is to write text in MS Word or other word processor, do equations in a LaTeX interpreter, and copy the equations and paste them as a bitmap into the Wordprocessor text file.
If Adobe Acrobat is installed and integrated properly, one should be able to convert the Word (or other wordprocessor) file into a pdf. This is the method I use at work.
Or one can do text and equations in LateX, but I don't know if the file can then be imported into Acrobat.
If you want to write something that is mathematically-intensive, use LaTeX directly, not any other kind of word processor. Then process the document with pdflatex, as graphic7 advises. LaTeX is not just a formula writer; you can write whole articles, papers, books,... with it.