Kiwix also supports copy-pasting feature. In order to do that, select a part of the text using the mouse and then choose Edit > Copy or just press Ctrl+C (⌘-C on Mac) from your keyboard. You can also do a right click on the text and choose "Copy" to copy the text or "Search for" to search the text in the ZIM file. Then you will be able to paste that text in any other application you want. If you want to select the whole text of a page, choose Edit > Select all or press Ctrl+A (⌘-A on Mac) from your keyboard. You can also right click anywhere in the page and choose "Select all".