Yes, you can do this, if you follow the process described in this article.
Leanpub only sells ebooks, not print books, and Leanpub ebooks can be updated at any time by their authors. This means that any Leanpub ebook you buy can change in the future. Our authors typically publish many versions of their books, because many Leanpub books are published while they are in-progress.
This means that you can not buy a Leanpub ebook yourself, download the ebook files and send them to your clients, because you may be providing them with an incomplete or unfinished ebook.
If you buy a Leanpub ebook on behalf of someone else, you need to give them a way to download the ebook themselves from Leanpub.
There are two ways to do this:
Buy the book as a "gift." Here are the instructions: http://help.leanpub.com/reader-help/i-would-like-to-purchase-a-book-as-a-gift-for-someone-else-how-can-i-do-this. When you complete the purchase, the recipient will receive an email with download links for each of the books you have purchased for them.
Buy multiple copies of the book. If you do this, you get a number of unique "tokens", one for each copy. These tokens can be emailed to your clients, who can redeem them online. Here are the instructions: http://help.leanpub.com/purchasing-help/how-do-i-buy-multiple-copies-of-a-book
We understand this process will not be acceptable to all booksellers. We're sorry if it means you can't buy Leanpub ebooks for your client. In that case, we would recommend that your client buy the ebook themselves, directly from Leanpub.