If you open the print page (print view) of a topic, the code bbcode still shows the "Select All" feature, which shouldn't be a problem. But once you click on that, you will get a javascript error:

selectCode is not defined

Additionally, the browser will jump to the top of the page.

I was able to fix it this way:
Open styles/prosilver/template/viewtopic_print.html
Find:

<link href="{T_THEME_PATH}/print.css" rel="stylesheet" type="text/css" />

Add before:

<script type="text/javascript" src="{T_TEMPLATE_PATH}/forum_fn.js"></script>