PDF invoicing plugin fails with internal server error

After evaluating pdf invoicing extension plugin in my local development environment, I tried to deploy it on my hosted website. It throws fatal error

– Generating invoice
– Sending invoice
– downloading invoice

After enabling debug mode following stack trace is returned.

Fatal error: Uncaught Error: Call to undefined function Dompdf\mb_internal_encoding() in /home/blueeyel/public_html/starlandscapers.com.au/wp-content/plugins/wpinv-pdf/includes/libraries/dompdf/src/Dompdf.php:274 Stack trace: #0 /home/blueeyel/public_html/starlandscapers.com.au/wp-content/plugins/wpinv-pdf/includes/libraries/wpinv-dompdf.php(16): Dompdf\Dompdf->__construct(Object(Dompdf\Options)) #1 /home/blueeyel/public_html/starlandscapers.com.au/wp-content/plugins/wpinv-pdf/includes/class-wpinv-dompdf.php(29): wpi_pdf_dompdf(Object(Dompdf\Options)) #2 /home/blueeyel/public_html/starlandscapers.com.au/wp-content/plugins/wpinv-pdf/includes/pdf-invoices-functions.php(170): WPInv_DOMPDF->writePage() #3 /home/blueeyel/public_html/starlandscapers.com.au/wp-content/plugins/wpinv-pdf/includes/pdf-invoices-functions.php(116): wpinv_pdf_generate(Object(WPInv_Invoice)) #4 /home/blueeyel/public_html/starlandscapers.com.au/wp-includes/class-wp-hook.php(288): wpinv_pdf_generate_pdf_invoice(Array) #5 /home/blueeyel/public_html/starla in /home/blueeyel/public_html/starlandscapers.com.au/wp-content/plugins/wpinv-pdf/includes/libraries/dompdf/src/Dompdf.php on line 274

Please help me fix it.