When I am trying to convert spl file directly through command line then its working but when I am trying to convert through application(At client side) it's not working and showing "Invalid spooler file". Please find attached spool file for your reference.
Thanks for your sample SPL file, I tried to convert your SPL file to PDF file just now, everything is fine.
Converter Command Line can be downloaded from following web page,
after download it, I tried following command line in my system, I could get a PDF file without any problem, please look at the converted PDF file in the attachment,
spl2pdf.exe D:\downloads\00494.SPL D:\downloads\00494.pdf
Thank you for choosing 'VeryPDF Converter Command Line' product.
"D:\downloads\00494.SPL" ==> "D:\downloads\00494.pdf"
[Message] #1 Page: 1, FilePos: 100
[Message] Found 1 pages...
[Message] Extracting page 1 of 1...
[SPL Document Name is]: Crystal Reports - GST POS Invoice.rpt
SPL: dmCopies is: 1
SPL: dmCollate is: 0
SPL: dmDuplex is: 0
[OK] Create "D:\downloads\00494.pdf" file(s) successful.
Please also look at the screenshot for the converted PDF file at below,