NConvert 6.21 (build 18 December 2012) delete input pdf

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NConvert 6.21 (build 18 December 2012) delete input pdf file
I type command
nConvert - out jpeg - q 65 -xall mypdf.pdf
I get message 'Error: Don't know how to read this picture (mypdf).pdf)'
and mypdf.pdf was delete.

I try another version Nconvert 6.21 (build 23 October 2012) - i get the same error message but input pdf file stay alive.

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