You might think it pretty easy to create documents for use in collaborative working - just use your favourite word processing or text hacking tool, image editor, music or sound creator. But, not everyone has or wants to use MIcrosoft Office, Photoshop, the Apple tools, or what you think is an ideal sound hacking tool. Going to the free, open source, tools doesn't fix the problem, as they are likely to use formats that change over time. And, you can't be sure everyone is using the same versions of the tools. So, what do you do?
Final delivery versus Collaboration
There are a number of document formats used for 'final delivery' of documents, Adobe Acrobat Reader PDF format (read-only) is one of those, and JPEG images are another. Adobe design the format, and while Microsoft may tinker with things to make PDFs editable this is not portable to, for example, standard Linux tools. JPEG isn't suitable except for final delivery because it is a 'lossy' format, and every edit cycle further degrades the image. (MP3 has similar problems for audio.)
Future-proofing your documents
Simple text, without things like emphasis (bold, italic, underline, strikeout), or text size changes, is best transferred as plain-text, ASCII (Latin 3, ISO 8859-3) or UTF-8. Tables can be done using CSV. Images require PNG. (For audio you probably want FLAC.) For more complex documents RTF is sometimes used (editors of publications may request this), some sort of mark-up format (such as Markdown), or even (simple, non-interactive) HTML. If MS Word files need to be used then using "Save As" to create Word 97 format files has often proved to be workable. Sometimes using table-to-text tools, and saving as plain-text, a blank line between paragraphs, two blank lines between sections, works well.
Microsoft and Apple
Anyone creating collaborative documents needs to think seriously about avoiding requiring Microsoft (or Apple) tools to be used; they are in the business of selling more MS (or Apple) stuff, not supporting the collaboration process. Anything which involves editing complex documents, intended for final delivery, is also best avoided.