Suggestion: You can add an additional line of code to the robots.txt file that specifies which PDF files should not be displayed in search engines. You can also use the ‘noindex’ meta tag to specify which pages should not be indexed by search engines.
Answer: Adding additional lines of code to the robots.txt file will not be overwritten when Concrete CMS is updated, so this is a viable solution for preventing PDF files from being displayed in search engines. However, it is important to note that the ‘noindex’ meta tag should also be used to ensure that the desired pages are not indexed.