in different iPhones i discovered that mail app no longer runs PDF capability. it just launches the contextual menu asking what app should i want to use to read the PDF. From there, if i choose "copy on Acrobat reader" because i have it, PDF works. Removing the Adobe app didn't save the thing.
Same PDF works on other devices running same account, also works on Message app but there is nothing to make it happen under mail. Also strange if you try to force clicking on "quick view" it says the PDF is empty despite it sees the real lengh on the mail message.