Hacerle means to ask someone a question. The "le" is a object pronoun which corresponds with the "usted" The "le" just further identifies to whom you are asking the question. Because hacer is not conjugated, you can attach le to the end of it. Hope that makes sense! :)

También se puede decir : ¿Puedo hacerle unas preguntas ahora? y omitir "a usted". O decir : ¿Le puedo hacer unas preguntas ahora?

Hello, in this page "http://lema.rae.es/dpd/" (Diccionario Panhispánico de Dudas). if you search for the word "le", you will find an exhaustive explanation of the use of "le" in your sentence in the section 5.2.a). The general explanation is: contrarily to many other languages, as english and german, for example, in spanish, the indirect object represented by a tonic complement is usually duplicated in the form of an atonic pronoun (in this case LE). See, for example, this sentences: No (les) da importancia a los problemas; (Les) he contado nuestro secreto a unos amigos; (Le) han denegado la beca a Juan; (Le) he dicho la verdad a mi madre. In these cases, le/les refers to a los problemas, a unos amigos, a Juan, a mi madre, respectively. It's use can be compulsive or optional (see the website I cited), depending on the cases. In the case you propose: "Puedo hacerle a Usted unas preguntas" it is compulsory to use LE (but you could omit "a usted": "¿Puedo hacerle unas preguntas?")