5. The method of claim 1 , wherein the first interpreter is Adobe PDF Print Engine (APPE) and the second interpreter is a Postscript interpreter, wherein step (a) includes detecting a version of the PDF by checking the document header without analyzing a content of the document; and wherein step (b) includes: (b1) if the version of the PDF document determined in step (a) is one of a pre-defined plurality of PDF versions, selecting only the APPE interpreter to be used to interpret the PDF document without analyzing the content of the document; and (b2) if the version of the PDF document determined in step (a) is not one of the pre-defined plurality of PDF versions, performing steps (b3) to (b5) for each page of the PDF document: (b3) determining whether the page contains transparency data; (b4) if the page contains transparency data, selecting the APPE interpreter to be used to interpret the page; and (b5) if the page contains no transparency data, selecting either the APPE interpreter or the second interpreter to be used to interpret the page.
5. The method of claim 1 , wherein the first interpreter is Adobe PDF Print Engine (APPE) and the second interpreter is a Postscript interpreter, wherein step (a) includes detecting a version of the PDF by checking the document header without analyzing a content of the document; and wherein step (b) includes: (b1) if the version of the PDF document determined in step (a) is one of a pre-defined plurality of PDF versions, selecting only the APPE interpreter to be used to interpret the PDF document without analyzing the content of the document; and (b2) if the version of the PDF document determined in step (a) is not one of the pre-defined plurality of PDF versions, performing steps (b3) to (b5) for each page of the PDF document: (b3) determining whether the page contains transparency data; (b4) if the page contains transparency data, selecting the APPE interpreter to be used to interpret the page; and (b5) if the page contains no transparency data, selecting either the APPE interpreter or the second interpreter to be used to interpret the page. 6. The method of claim 5 , wherein the pre-defined plurality of PDF versions include PDF/VT, PDF/X-4 or later.