Error: can’t send PDF file

Hi. The plugin is giving error to create PDF.
I use: [frontend-checklist name=”1″ cookie=”off” type=”pdf” title=”My Checklist” linktext=”Salvar em PDF”]

This page appears:

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; tFPDF has a deprecated constructor in …wp-content/plugins/frontend-checklist/fpdf/tfpdf.php on line 13

FPDF error: Some data has already been output, can’t send PDF file (output started at …wp-content/plugins/frontend-checklist/fpdf/tfpdf.php:13)