Nap apps doe GEO tiffs

The Tasmap mapping derive is now putting out the 1:25000 series in this format, and also as Google earth comatible files.
So, is there an app that allows you to import these maps and use them in the field? Second, if I download the google ones, can I use them when there is no internet connection.
I have an iPad2/4th generation with retina screen and 128Gb memory. I've uploaded the tiffs as pdfs so I can access them, but having to change maps is a bit tedious in the middle of something, a seamless segue from one to another would be very nice.
All help very gratefully received.
So, is there an app that allows you to import these maps and use them in the field? Second, if I download the google ones, can I use them when there is no internet connection.
I have an iPad2/4th generation with retina screen and 128Gb memory. I've uploaded the tiffs as pdfs so I can access them, but having to change maps is a bit tedious in the middle of something, a seamless segue from one to another would be very nice.
All help very gratefully received.