Automatic OCR Scan at startup

Hi, @ILLI_ICT, you're not letting anyone know what you're starting out with, but I can run down the file formats that do NOT automatically initiate the OCR process and then the one that does do what you want. 

If you open an already created PDF that has yet to have any OCR processing (a PDF of an image), it can only automatically start the OCR process if you want to Edit the document. At that point, the OCR process will start (one page at a time, which is annoying) because you cannot edit what is not text.

If you scan and save the documents into the following formats, you must initiate the OCR process as an extra step: JPG, PNG, WBM, and GIF (at the top of my head, that's it.)

If you scan and save the document in the TIF document, OCR will self-initiate.

As a Mac user, I never scan from within Acrobat. Keep in mind that Acrobat cannot scan. Rather, it uses the TWAIN technology of letting Acrobat access your scanner's native software to do the scan. Since Apple will not allow one application to operate a different application (as part of their anti-virus approach to things), it does let Acrobat, Photoshop, and other applications access Apple's Image Capture application, the worst scanning application I've ever seen. So, what I do is scan with either my scanner's software or via SilverFast (mostly a top-of-the-line photographic scanning software) and save the file in a folder on my desktop. From there, I can collect a set of files from a multi-page document and drag it onto the Acrobat icon in my Dock. At that point, Acrobat will ask me if I want each page as separate or a single multi-page document. After that (and here's the annoying part), Acrobat doesn't share the OS. It will dominate the computer until it has finished its OCR process. Depending on the length of the document, I wait, get a cup of coffee, or get lunch. 

I know that's a lot more than you asked for, but I thought it might help you. Lastly, if you want information on how to get the best quality scans for the best quality OCR, here's a blog I wrote for Adobe a number of years ago.

https://community.adobe.com/t5/adobe-community-professionals/scanning-clean-searchable-pdfs/m-p/4785435?page=1#M89

Good luck!