Contents contain doesn't work on a PDF

Greetings,
for an invoice in PDF format I've set the rule Contents --> Contain, then I've put the string of text, but when I check then the white cross inside the red round icon appears.
The strange thing is if I click on the icon in order to see the contents, then the string of text is there.
I've also tried copy/paste from the contents window, but the bad icon is still there.
I've tried with many strings of text that appear in the contents windows, but I get the same icon.
It's as like as Hazel doesn't detect the text inside the PDF, though it shows it.
How do I solve it?
TNX!
for an invoice in PDF format I've set the rule Contents --> Contain, then I've put the string of text, but when I check then the white cross inside the red round icon appears.
The strange thing is if I click on the icon in order to see the contents, then the string of text is there.
I've also tried copy/paste from the contents window, but the bad icon is still there.
I've tried with many strings of text that appear in the contents windows, but I get the same icon.
It's as like as Hazel doesn't detect the text inside the PDF, though it shows it.
How do I solve it?
TNX!