FineReader Engine 12 opens and saves image files in PDF as well as in the various image formats, but not PDF portfolio.
The PDF portfolio is currently not supported.
Transform Portfolio to regular PDF using the following command:
pdf2ps file.pdf - | ps2pdf - converted_file.pdf
Where "file.pdf" is the original Portfolio PDF. The result "converted_file.pdf" will be OCRable by means of FineReader Engine.