回答

生成数字证书并设置密码

# generate new .crt file, it's contained certificate & private key
openssl req -x509 -nodes -days 365000 -newkey rsa:1024 -keyout filename.crt -out filename.crt

# convert .crt to binar .p12 file
openssl pkcs12 -export -in tcpdf.crt -out filename.p12

# get private key from .p12 file, it will ask for passphrase/password, so the generated private key will be encrypted
openssl pkcs12 -in filename.p12 -nocerts -out filename.key

# get certificate from .p12 file
openssl pkcs12 -in filename.p12 -clcerts -nokeys -out filename.crt

利用TCPDF 签名

<?php
/** @var TCPDF $pdf */
$pdf->setSignature('file://PATH-TO-CRT-FILE', 'file://PATH-TO-PRIVATE-KEY-FILE', 'PRIVATE-KEY-FILE-PASSPHRASE', '', 2, $info);

github地址https://github.com/harryosmar/php-pdf-digital-signature