Maximum size for pdf attachment

I’m using your plugin on two websites, and on both I have the same problem. It seems that as soon as the pdf that is being created exceeds 90 kB it is not attached any more to the email.

I have tested this in different situations by shortening and lengthening the pdf, also with different types of text, and this seems to be the only reason.

Is there any way to increase of remove this size limit?

The page I need help with: [log in to see the link]