finder cannot open powerpoint or pdf files
When trying to open a powerpoint I get this message: PowerPoint. Powerpoint cannot read pptx file . a similar situation happens with PDF files
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What message do you receive when right-clicking on that PDF document and choosing Open With > Preview?
Single-click on that reluctant PDF document and press option+cmd+i to open a get info. Does it show a PDF version of 1.3 thru 1.7? What is the document creator?
If Powerpoint cannot open one of its own documents, then either the document is damaged, is not really a Powerpoint file, or someone created the Powerpoint document with a newer version of Powerpoint and a feature not implemented in your version.
Download and install the current (7.4.3) version of LibreOffice. You will need to right-click on the LibreOffice application icon and choose Open (once) to complete the installation. Open that Powerpoint document in it. Then save it as a Powerpoint 2007-365 presentation again. Then attempt to open that document in Powerpoint again. That may resolve the issue.
I have encountered MS Office documents that would not open in their own applications, but would after the preceding LibreOffice treatment.