Hi Thomas

There is no easy way to do this in Web Designer as far as I can find. I have used other software were it was available. But I have come across this option from this website

1.     
Resize your “print” image to the size required
on your webpage. To get an idea of the size required put a rectangle on your
page(keep this on the page as you will use this later as a placeholder). If you’re
using an icon from Web Designer then, place it on your page – with it selected
go to File – Export png and save it on your PC.

Thinking about this you can always use the "print" icon as your placeholder instead of the rectangle as you found out the placeholder image disappears.

2.     
Upload this “print” image to the root folder of
your website space. This folder is where your website .htm pages are uploaded
too. You can use a third part FTP client such as Filezilla or Core FTP

3.     
Back to the placeholder rectangle on your page, right
click - Web properties – Placeholder Tab. Click the HTML code body button and
in the pop up window copy and paste the following

4.     
<a href="whatever.htm"
onClick="window.print();return false"><img
src="http://www.yoursite.com/print.png"></a>

5.     
Change the website address and “print” image
name to your own. You don’t have to have your website address, just the “print”
image name, but you will not be able to preview it in Web Designer, or until you
have uploaded to preview.

I hope this helps

Dond