Print paper size

 If your printer has the option to register paper information (found in either Feed settings or Cassette settings depending on the model) and the printer setting to detect paper mismatch is enabled, you can specify the size and type of paper loaded in your printer. AirPrint will use this information when you print a document or a photo. If your printer does not have this option, then the menu may not be available

Example of paper size selector option (this may not be available for every printer):

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