Using Aspose PDF for Java I discovered that multiple threads cannot access the same document in parallel when using Page.accept. Page.accept calls TextAbsorber.visit which seeks within the parent Document. If this occurs while another page is being processed, text can be dropped or an exception can be thrown.
We were processing each page of a PDF in parallel when we encountered this problem. For the time being we have synchronized use of Page.accept but I thought you might like to know about this limitation.
The closest related post I found to this was this one: Does the latest release of Aspose.Pdf support multithreading?