Hello Evobio2013 and welcome to the ArtRage forums

Which iPad version do you have?
The latest version, ArtRage Vitae Mobile, allows canvases up to 4096px x 4096px.
This should be adequate for printing at approximately A3 paper size at 300dpi and still get good results when viewed at typical average wall print viewing distances.
If the viewing distance is to be further, then larger print sizes could still be possible as generally the dpi needed drops as distance increases.
If you have the old mobile version, then yes, without having the desktop version to play the painting back as an ARScript, your options are limited for printing large paintings.