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At random Explorer will launch a thread which eats 50% of CPU.

I've captured this stacktrace:

enter image description here

Why is Acrobat PDF Reader reading my documents in the background? It seems like Explorer is scanning my documents?

Have you experienced such behaviour?

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migrated from Sep 30 '09 at 12:45

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How did you produce that stack trace? Did you run Acroread yourself? I'm smelling malware here... – Kage Sep 30 '09 at 12:36
Could be an indexing service. – silky Sep 30 '09 at 12:44
Adobe's acrobat reader is a horribly resource heavy piece of software if all you need to do is read pdfs. I'd recommend switching to Sumatra PDF reader or foxit reader either of which will open pdf's much more quickly and use far less cpu and ram – Col Aug 12 '11 at 22:45

With PDFLTerm in the stack trace, I'm guessing you closed (terminated) a PDF opened in Acrobat. You can pinpoint exactly what Acrobat is doing when a thread is spawned using Process Monitor from Sysinternals. When you see CPU usage spike, check the time and go to your Process Explorer window. Make sure AcroRd32.exe is the filter so you don't see all the other system activity. Look for the last "ThreadCreate" in the Operation field and you can see exactly what happened following the threads creation (what files were opened, what registry values were written, etc...)

enter image description here

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I work in a company that uses Adobe Reader a lot, and this is a common occurrence if Adobe isn't closed properly, this leaves it running in the background

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But it would be left using a full CPU ? Strange. – Gnoupi Sep 30 '09 at 12:57
IF not closed properly then it will "spaz" out – admintech Sep 30 '09 at 14:34
@admintech How do you not close Adobe Reader properly? Or is it a latent bug in the software? – Ben Richards Aug 11 '11 at 6:23
1. Open Acrobat or Adobe Reader. 2. Select File > Exit. – admintech Aug 11 '11 at 10:30

Acrobat Reader is left opened in background, if it is used to display PDF in browser, as explained on this link :

However, I don't know why it would require a full CPU activity.

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