Hi,Whenever I am trying to view thumbnail of PDF,  after upload it in document and media, it shows below error for each PDF in log. kindly provide the resolution for resolve this issue.

For us to come up with a solution, please start with

• information about the exact version of Liferay that you're asking about
• the full unabbreviated error message
• (if there's a stacktrace: Include it)
• Does this happen for any pdf? (try to upload trivial ones, from different sources)
• Do you have any specific configuration in your system, e.g. imagemagick (which can be used for preview generation)
  

Hi Olaf Kock,
Thanks for your reply, pls find below detail.1) Liferay Version- 7.1 (community edition).2) Error Message
WARN  [liferay/document_library_pdf_processor-1][BaseProcessorMessageListener:40] Unable to process file version 36551
java.lang.NullPointerException
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1012)
    at com.liferay.petra.process.ProcessUtil.execute(ProcessUtil.java:55)
    at com.liferay.portal.image.GhostscriptImpl.execute(GhostscriptImpl.java:75)
    at com.liferay.portal.kernel.image.GhostscriptUtil.execute(GhostscriptUtil.java:26)
    at com.liferay.portlet.documentlibrary.util.PDFProcessorImpl._generateImagesGS(PDFProcessorImpl.java:563)
    at com.liferay.portlet.documentlibrary.util.PDFProcessorImpl._generateImagesGS(PDFProcessorImpl.java:499)
    at com.liferay.portlet.documentlibrary.util.PDFProcessorImpl._generateImages(PDFProcessorImpl.java:397)
    at com.liferay.portlet.documentlibrary.util.PDFProcessorImpl._generateImages(PDFProcessorImpl.java:429)
    at com.liferay.portlet.documentlibrary.util.PDFProcessorImpl.generateImages(PDFProcessorImpl.java:109)
    at com.liferay.document.library.kernel.util.PDFProcessorUtil.generateImages(PDFProcessorUtil.java:34)
    at com.liferay.portlet.documentlibrary.messaging.PDFProcessorMessageListener.generate(PDFProcessorMessageListener.java:30)
    at com.liferay.portlet.documentlibrary.messaging.BaseProcessorMessageListener.doReceive(BaseProcessorMessageListener.java:36)
    at com.liferay.portal.kernel.messaging.BaseMessageListener.receive(BaseMessageListener.java:26)
    at com.liferay.portal.kernel.messaging.InvokerMessageListener.receive(InvokerMessageListener.java:74)
    at com.liferay.portal.kernel.messaging.SerialDestination$1.run(SerialDestination.java:58)
    at com.liferay.portal.kernel.concurrent.ThreadPoolExecutor$WorkerTask._runTask(ThreadPoolExecutor.java:752)
    at com.liferay.portal.kernel.concurrent.ThreadPoolExecutor$WorkerTask.run(ThreadPoolExecutor.java:664)
    at java.lang.Thread.run(Thread.java:748)

3) It is for any PDF.4) In Server Administration >> External Services,  PFA screen shot

<p>Enabling ImageMagick and GhostScript provides document preview functionality. (Enable Checkbox checked)</p>

<p>Path:-&nbsp;/usr/local/bin:/usr/share/fonts/default/ghostscript:/usr/share/fonts</p>