Replace Zend_Pdf with html2pdf tool

Nobody has claimed this yet.

Top voted suggestion in Magento idea exchange forum: https://community.magento.com/t5/Magento-2-x-Feature-Requests-and/Invoice-shipment-credit-memo-PDFs-Remove-Zend-Pdf-replace-with/idi-p/45879

Given that the current invoice, shipment and credit memo PDFs look the same as in Magento 1 and PDF's are always a bit of a nightmare to customize for the merchants:

I suggest to replace the PDFs with a html2pdf tool. Actually the preview of the invoice looks already really nice in the backend, so this could just be converted to pdf.

Affected entities: Invoice, shipment, credit memo PDFs

This would maybe also help the problem Hirokazu Nishi mentioned in his tweet:

"Magento2 still use LinLibertine font. It’s only for Alphabets. To change PDF font, we still have to rewrite some classes..."

This idea resulted from a tweet/discussion here:
https://twitter.com/hirokazu_nishi/status/770282916819578881
https://twitter.com/rescueAnn/status/770338589326635008
https://twitter.com/benmarks/status/770339381995384832

Start by reviewing the linked Magento idea exchange discussion and the existing invoice, shipment, and credit memo PDF generation paths. Define the replacement's scope and a verifiable result for all three PDF types, including whether the backend invoice preview is the source; the issue names no files or tests, so repository investigation is required.

Written by the indexing model from the issue text.