Some PDF documents not loading for editing using persits.pdf tool

Question

I have a requirement to edit the fields in pdf document using persits.pdf tool.

here is my code.

 

 

PdfManager objPDF = new PdfManager();

PdfDocument objDoc;

objDoc = objPDF.OpenDocument(cert.FileLocation + cert.CertificationFileName);

 

 

when the execution comes to opendocument() method it throws exception.

 

Source array was not long enough. Check srcIndex and length, and the array's lower bounds.

 

this exception is  coming only for some documents. some are working fine.

 

Thanks in advance.