Yes, you can plot an PDF file with searchable text from Allegro PCB Designer.
You need some kind if PDF printer installed. I recomend Adobe PDF Distiller or Writer.
Then you need to open the Allegro Plot setup (File --> Plot Setup), select the Windows tab and check the Vectorized Font box. The fill in desired font.
When you print select the PDF printer and you should be able to schearch inyour PDF.