Dear somos,
Thanks for your inquiry and sorry for late reply as weekend.
From the exception information, you were using Free Spire.Doc which has limitation, please upgrade to the latest commercial
Spire.Doc Pack(hot fix) Version:5.8.70.
And here is information of Spire.Doc V5.8.70 for checking.
1)Spire.Licesne.dll V1.3.6.40
2)Spire.Doc.dll V5.8.70.3040
3)Spire.Pdf.dll V3.8.227.3040
If there is any question, please let me know.
Sincerely,
Betsy
E-iceblue support team