Hi Tatiana,
I am glad to hear that you do have the option now for save your scanned image as a PDF from your LaserJet.
Now with the the DeskJet F4210, you do have the full featured software installed, so theoretically speaking it should have the option for saving as PDF, as long as you have a full up to date version of Adobe Reader. To make sure that you do have the latest full version of Adobe Reader, I have included a link to 'Adobe Reader' to download the software.
After installing the latest version of Adobe Reader, try scanning a document from the HP Solution Center. Do you see an option for PDF, or PDF Searchable (*.pdf)?
Looking forward to your reply.