The initial state of any rich text editor in Pressero admin is blank and the underlying code is also blank. When you type text, highlight it and choose to turn that text into a heading (as example), the code behind what you are seeing is very simple. <h1>Heading text</h1>.
In the event that you select text on a website, in a Word document, in a google document, etc., and copy it and then paste it into any rich text editor not only is the text being pasted but also the underlying html code. The html code can be very complex and it cannot be effected by the current skin.
This is a problem inherit with ALL rich text editors online, not just Pressero. It is best to never copy/paste directly without first removing any of the formatting. You can do that by copying the text and then pasting into a plain text editor such as Notepad. Then copy that clean text and paste into the Pressero text editor.
If you have already pasted text in Pressero and are experiencing problems, the best function to fix this is to use the "Clean Formatting" option in the editor (paintbrush icon).
Another option to fix this would be to:
Copy the text from the Pressero WYSIWYG edit area and paste it into a plain text editor (Notepad, etc.). This will "clean" (remove) the extra MS Word html.
Copy the text from the plain text editor,
Highlight the text in the Pressero WYSIWYG editing area and paste the new text. This will remove the previous Word infested text. Save. If you need to format the text, do so using the controls built into the Pressero WYSIWYG editor.