To search a PDF, the software needs to run OCR - optical character recognition - which looks at the shapes of the letters and works out what the text says, then embeds that text in a hidden layer beneath the image (or converts the image into real text). Adobe Reader cannot do OCR - if the software that came with your scanner doesn't do it (and many will, as an option when you make the scan), you'll need to use Adobe Acrobat or a similar program.
Should be the Scanner problem.
Think I should invest a better scanner with OCR.
But if the Scanner withour OCR is there any way i can download it from any site?
There are software programs that perform OCR on images of text. I don't think any of them is free, but I may be wrong.