pdf_files folder being cleared out when reports execute

Admins please help. I don't know where to locate the file which causes this to happen but have been trying to troubleshoot this report error for several days.

I went into the server from the hosting file manager and added a file 'testpdf.pdf' to the /company/0/pdf_files/ directory manually. I called the pdf file successfully from the browser by navigating to the url. The file was successfully added to the directory and was displayed properly.

I then went back into FA and tried to execute a sales report (but this problem happens with all reports). The pop-up to display the report shows a 404 error (which I have written about in the reporting section of this forum). I then looked at the /pdf_files/ directory again and there is no file called testpdf.pdf any longer. It appears that FA is wiping files from that directory when it tries to make a report. The only file which does not get deleted is the index.php in the directory which was written by the installation.

How can I disable the program from deleting files in that directory?? I would rather have to go into the server manually each week and delete the old reports than not be able to use the reports feature at all.

Please any advice would be appreciated. I am certain there must be someone here who knows of a line of code which cleans that /pdf_files/ directory out and I need to remove it asap.