Possible PDFLib-lite replacement :
PowerPDF is a VCL to create PDF docment visually. Like QuickReport, you can design PDF document easily on Delphi IDE. PowerPDF requires Delphi 2007 or later.
PowerPDF has been ported to lazarus, and is present in the lazarus code and components repository.
I've looked a bit into combining lazarus and c++ code, and this has some caveats.
Lazarus can use C code directly, but the C++ code needs to be declared as extern "C" and adhere to the C standard.
For C++ code that doesn't use this, a wrapper can be used that translates between lazarus and C++ code.
an example of such a wrapper is the code Lazarus uses to access Qt functions.
Lazarus executable code can be treated as a C library by other programs and doesn't require special wrappers or bindings.
We will have to look at each C++ sourcefile and determine what is better solution :
port the code to lazarus or create a wrapper.
I expect all of the code that uses VCL components or win32 functionality will need to be ported.
For C++ code that uses functions from the external libraries we'll have to check if gcc can link them to the external libraries.
If that's not possible, we can either change the C++ code to become compatible with gcc, or port this code to lazarus.
For those wondering why we just don't use gcc to compile everything : afaik as i know there are no crossplatform versions of the VCL and win32.
Both are proprietary software, and their owners (Codegear and Microsoft) show little interest in crossplatform support.