A Custom Page is very similar to the Basic Page. I would even say that it is exactly the same, but the Basic button/app is added automatically as a Welcome page when you create a new subpage. It contains the same features available on the toolbar.

Below is the Internal Training Sequence I used as a guide while training for the rST6 product. I have inserted it as a media embed. This is done by uploading the file (PDF, preferably) to the File Manager. Right click the file, click Show URL, and copy it directly instead of clicking the Copy button. Then paste it here after clicking the Insert Media Embed setting on the toolbar.