How to genrate a pdf format from eagle to print it?

Go to View>Layer Settings... and select the layer or layers that you want to print. Then go to File>Print... Set Scale factor to 1 and select paper size then print. In File Print Settings maybe you have to select PDF printer. If you install FoxIt Free version you get a PDF Printer in File>Print Setup.

You can also Export to clipboard in the Export dialog (File>Export>Image...). Then use what ever image editor you have to open the clipboard, e.g., PhotoShop, and save as pdf.

John