I'm not familiar with the website you mentioned, however what you are seeing in your documents is markup language which is how documents are formatted.
Depending on what software you are reading these documents in, there ought to be a setting in that software to not display markup languages, and instead only display the actual text or images in the document itself.
If you let us know what application you are using to read the copied documents then I'm sure someone can help you out with figuring out how to turn off the feature which currently is displaying the markup code, or you could probably Google search yourself ' how to turn off markup ' in the application you use to read the documents.