For some reason, when there are many products in an order, the PDF invoice generated by Prestashop backoffice and user front-end does not display all the products ordered.
In this case, there were 49 products.
Opening the generated PDF in Acrobat Reader triggers a warning message about it unable to display correctly and other PDF readers had the same issue.
Tried searching for solutions that suggested making changes to files in classes/pdf/PDFGenerator.php and tools/tcpdf/tcpdf.php, etc, but none worked.
An unexpected workaround.
After downloading the same PDF file, I used Chrome browser to open it and it displayed properly WITHIN the browser! No formatting error or missing content. I posted the same file to my gmail account and opened it without a glitch too.
I generated another PDF file by printing the one displayed correctly by Chrome browser using PrimoPDF (http://www.primopdf.com/) and the new file worked like a charm.
Although I didn’t find a solution to fix the issue in Prestashop, this workaround will do for now.