I write all the text I can using TeX (PDFLaTeX to be exact). This leads directly to a PDF document without intermediate steps. The graphics are done using Metapost because I'm better at programming than at drawing. Metapost produces Postscript-like files which some LaTeX macros then read and directly integrate into the PDF output.
The result in this case is a PDF with 114 pages which is only 934051 bytes in size. Just about 8kB for each page. Given that the text is multi-column and the numerous graphics in the text this is amazingly small.
I mentioned before how badly OO.org sucks at exporting graphics. I bad all the other word processor, spreadsheets, etc suck just as badly. Also generated PDFs for text is much, much bigger.
My guess is that if I'd written the document with OOO.org the size would be north of 4MB, probably significantly more. I cannot understand why people do this to themselves and, more importantly, to others.