Hello,
Your username doesn't have any license tied. Please send to contact[at]phpdocx.com the username or email of the user that purchased the license you are using.
About your questions, please note the following:
- phpdocx doesn't use TCPDF to transform DOCX to PDF. On https://www.phpdocx.com/documentation/conversion-plugin you can read all information about the available conversion plugins. We recommend check the conversion plugin you were using in your previous installation and use the same settings for the new installation.
- To sign a PDF you need to use SignPDF or SignPDFPlus classes as detailed on https://www.phpdocx.com/api-documentation/digital-signature-package/digitally-sign-docx-pdf-with-PHP, not the TCPDF_Lib.php class. We recommend you check and run the samples included in the package (examples/DigitalSignature folder).
- The same when merging PDF files. Instead of TCPDF_Lib.php, please use MultiMerge (https://www.phpdocx.com/api-documentation/docxutilities/merge-pdf-documents-with-PHP).
Regards.