Hide Authoring info on certain pages/nodes
You could add a checkbox field to the content type, and adjust the node.tpl file. If the box is not checked, don't print submitted by.

Add the field to all content types (sounds like thats what you asked for) and remove it from each display under "Manage Display".

Then, in template.php, implement template_preprocess_node:

mythemename_preprocess_node(&amp;$variables) {
  $node = $variables['node'];

  // here we are creating a brand new variable
  // true, unless otherwise set by editors
  $variables['show_authoring'] = TRUE;

  // the field exists on the node object
  // update our custom variable to this field value
  if (isset($node-&gt;field_show_authoring)) {
    $variables['show_authoring'] = $node-&gt;field_show_authoring[LANGUAGE_NONE][0]['value'];
  }
}


If you want all nodes have this, you can copy in node.tpl.php to your theme or edit the one in your theme if it exists, and do:

&lt;?php if ($display_submitted &amp;&amp; $show_authoring): ?&gt;
  &lt;div class="submitted"&gt;
    &lt;?php print $submitted; ?&gt;
  &lt;/div&gt;
&lt;?php endif; ?&gt;


You could remove $display_submitted if you wanted to, I left that there in case you wanted control in the future to completely disable showing authoring for certain content types, like Webform for example. My syntax should be correct but I did not have a chance to test this in a sandbox.

See more: 


template_preprocess_node
How do I create a variable for my template file?
Preprocessing function for node.tpl.php