search in windows

I write a lot of small story´s in Libre Office. I name them. Some I export as a pdf to send to people of whom most dont know LO.

Later I try to find the story, and think of a word that is specific to that story. So I go to the folder containing all those story´s and search with the word. ( I use windows 8.1 ) So windows searches
Most of the time windows does not find the LO aricle but if I have exported to PDF ( they are in the same file ) windows finds the story.
I can do a cheque, the two storys are in the same folder, the pdf and the odt and only in the pdf the specific word is found.
Why ? What do I do wrong ?

I have Windows 10 but I don’t use Windows search function so I can’t help with details however there are a couple of sites that tell you how to expand the types of text files for Windows to look within and the instructions look straightforward: https://www.howtogeek.com/99406/how-to-search-for-text-inside-of-any-file-using-windows-search/ , How to force Windows 10 to search inside files for text

Finding by searching content of files requires an operating system functionality to open the file and to create an index, hence the operating system’s index facility must be aware / configured:

  • that it should create the index of the content for a specific file type (by file extension) --and–
  • how to open the specific file(s), which should be indexed

On Windows 10 (got no Windows 8.1) you can find the proper setting in Windows -> Settings -> Search -> Searching Windows -> Advance Search Indexer Settings (and on Windows 10 and LibreOffice 6.4.5 the proper entries to index content of ODF type extension are set),

I have now followed the advice, the indexing took a very long time, no result.
I put in a search for the word “ Pietje” and I am given the pdf, not the odt.

It wasn’t meant as an advice but an explanation and in fact stating that your question is not related to LibreOffice - it is a matter of your operating system, while this site is about questions on LibreOffice usage.

Agree, It is not a LibreOffice problem.
Other question. Since windows finds words in Pdf, and a lot of my small story are exported to pdf.
Each time I change a story, LibreOffice asks me to save the change. Fine, great. Could I also automatic save the change in de Pdf? So the pdf receives a change / addition also ?

No - you can’t, these are two files. It is possible to create a macro exporting to PDF and binding that macro to event Document has been saved, which results in saving the writer file also creates a new PDF.

Windows cannot search inside a file while LibreOffice has it open.

LibreOffice 6.3.6.2 (x86); OS: Windows 6.1.