在iOS中对PDF文档进行数字签名

recently I was assigned an iOS project, where I need to digitally sign a pdf document using a key that the application will download from a server. I don't yet have a clear idea of the process involved in signing documents, what I know until now is that I will be signing my pdf using a private key file provided to me, and then the verification will be done using the public key version of the same file.recently I was assigned an iOS project, where I