thats if they open at all. Sadly the way you are currently generating the popups do not work in touch devices. I've only tested on iPhone but all you get (even when you know where to tap) is a momentary highlight but then nothing happens -- not via short tap or either via a long hold where you'd usually get the prompt to open in a new tab.
Popups like this are unfortunately not friends of mobile. The safest bet would be to simply open the file via a standard link to the image or to another web page. Alternatively, you can play around with this image popup modal to see if that works in your situation.
http://fofwebdesign.co.uk/template/_...odal-popup.htm
The image will resize but is zoomable to some degree (though probably not enough to make a scanned letter big enough to read) but you might be able to get a reasonable result of you edit/remove background:cover; for the popup img in the CSS
Bookmarks