Change multi-font attributes on preferredContentSizeChanged notification. From this: http://stackoverflow.com/questions/18928620/handling-uicontentsizecategorydidchangenotification-for-nsattributedstring-in-ui

preferredContentSizeChanged.m

- (void)preferredContentSizeChanged:(NSNotification *)aNotification
{
    UITextView *textView = <the text view holding your attributed text>

    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithAttributedString:textView.attributedText];
    NSRange range = NSMakeRange(0, attributedString.length - 1);

    // Walk the string's attributes
    [attributedString enumerateAttributesInRange:range options:NSAttributedStringEnumerationReverse usingBlock:
     ^(NSDictionary *attributes, NSRange range, BOOL *stop) {

         // Find the font descriptor which is based on the old font size change
         NSMutableDictionary *mutableAttributes = [NSMutableDictionary dictionaryWithDictionary:attributes];
         UIFont *font = mutableAttributes[@"NSFont"];
         UIFontDescriptor *fontDescriptor = font.fontDescriptor;

         // Get the text style and get a new font descriptor based on the style and update font size
         id styleAttribute = [fontDescriptor objectForKey:UIFontDescriptorTextStyleAttribute];
         UIFontDescriptor *newFontDescriptor = [UIFontDescriptor preferredFontDescriptorWithTextStyle:styleAttribute];

         // Get the new font from the new font descriptor and update the font attribute over the range
         UIFont *newFont = [UIFont fontWithDescriptor:newFontDescriptor size:0.0];
         [attributedString addAttribute:NSFontAttributeName value:newFont range:range];
     }];

    textView.attributedText = attributedString;
}