First you check with your printer what type of PDF they want and whether they want single pages and whether they want crop marks.
If you don't know what the printer wants and you have to proceed without their advice and you're printing commercial litho:
Select within InDesign: File > Export to Adobe PDF Presets > PDF/X-4.
Within Acrobat on the left hand side of the Export PDF Panel, under General tick Pages (not Spreads), and under Marks and Bleeds tick Crop Marks, and any other printers marks you want to include, and make sure you also tick Use Document Bleed Settings.
Then proceed to Export.
How do I see the crop marks in my pdf doc.
Open it in acrobat.