The Snap&Read tool bar is disappearing after opening a PDF in Chrome because the PDF is opening in view mode; and not as a reader. You will know if you are in preview mode if you see an icon that looks like a box with an arrow coming out of the top right. It is the pop out icon. If you pop the pdf into it's own browser tab, Snap&Read Universal will be able to see it.
Also, if you load your web page before you turn on Snap&Read, Snap&Read will not see the page. In that case, simply refresh your page and the menu bar should show up.