Tim from Louisville, Ohio writes:
If I have Ubuntu and my correspondents do not: if I sent them an attachment using a word processing or spreadsheet program, will they be able to open it?
As long as you save it in a file format their computer can understand, there should be no problem. If you use a program like LibreOffice to create documents or spreadsheets you will be able to save it in a file format that Windows or Mac systems can read. Check out this informative article on LibreOffice to learn more. 
The same would also hold true for image files. An image saved as a jpeg, tiff or gif on a program like Pinta , could be opened in any other program that can read those files. Pinta is a free program that is very similar to Paint.net.
Office Libre and Pinta are good examples of the variety of free program available for the Linux OS. They will do many of the same things that programs costing hundreds of dollars do. And with a free operating system and free programs, the cost to you is basically the time you’ve spent installing Linux and setting up your system.