encode': "\\x90" on UTF-8 (Encoding::InvalidByteSequenceError) Prawn - ruby

Question

i'm using prawn to generate a pdf document with all the code from my application (juridic issues) and i'm having a actual hard time that has to do with the fonrts implemented, someone knows how could i solve this?
For reference, the error code is
`[...]encode': "\\x90" on UTF-8 (Encoding::InvalidByteSequenceError)
and the code that generates the error seem
pdf.text hash.keys.first, style: :bold
I have configured the font to Times-Roman, any other generate encoding errors as well
pdf.font "Times-Roman"
And i've already tried to append encode('utf-8') and force_encode('utf-8') at the strings that are genereting the errors
EDIT:
For specifics, some of the strings that are generating problems are
function removeEspeciais($string) {
// matriz de entrada
$what = array( 'ä','ã','à','á','â','ê','ë','è','é','ï','ì','í','ö','õ','ò','ó','ô','ü','ù','ú','û','À','Á','É','Í','Ó','Ú','ñ','Ñ','ç','Ç');
// matriz de saída
$by = array( 'a','a','a','a','a','e','e','e','e','i','i','i','o','o','o','o','o','u','u','u','u','A','A','E','I','O','U','n','n','c','C' );
// devolver a string
return str_replace($what, $by, $string);
}
Or
17.1. Nfe.png
�PNG