I think cause from Ghostscript. This is error message.
-sFONTPATH=C:\\Windows\\Fonts
-sDEVICE=pdfwrite
-dPDFSETTINGS=/default
-dCompatibilityLevel=1.4
-r600x600
-dProcessColorModel=/DeviceCMYK
-dAutoRotatePages=/PageByPage
-dCompressPages=true
-dEmbedAllFonts=true
-dSubsetFonts=true
-dMaxSubsetPct=100
-dConvertCMYKImagesToRGB=false
-sOutputFile=C:\\Users\\Uthen\\Desktop\\ทดสอบ.pdf
-dEncodeColorImages=true
-dAutoFilterColorImages=true
-dEncodeGrayImages=true
-dAutoFilterGrayImages=true
-dEncodeMonoImages=true
-dMonoImageFilter=/CCITTFaxEncode
-dDownsampleMonoImages=false
-dPreserveOverprintSettings=true
-dUCRandBGInfo=/Preserve
-dUseFlateCompression=true
-dParseDSCCommentsForDocInfo=true
-dParseDSCComments=true
-dOPM=0
-dOffOptimizations=0
-dLockDistillerParams=false
-dGrayImageDepth=-1
-dASCII85EncodePages=false
-dDefaultRenderingIntent=/Default
-dTransferFunctionInfo=/Preserve
-dPreserveHalftoneInfo=false
-dDetectBlends=true
-f
C:\\Users\\Uthen\\AppData\\Local\\Temp\\PDFCreator\\PDFCreatorSpool\\~PSB51B.tmp
05-Jan-10 9:45:42 AM: Error: GPL Ghostscript 8.70: **** Could not open the file C:\\Users\\Uthen\\Desktop\\?????.pdf .; **** Unable to open the initial device, quitting.;
05-Jan-10 9:45:42 AM: Time for converting [PDF without encryption]: 00:00:00:369