Freud seems to have been frustrated with the reception the first edition of the book received from the other professionals to whom he initially directed it. In the preface to the second edition, he mocks these readers and indicates that he is now hoping for, and grateful to, a wider audience:
If there has arisen a demand for a second edition of this rather difficult book before the end of the first decade, I owe no gratitude to the interest of the professional circles to whom I appealed in the preceding sentences. My colleagues in psychiatry, apparently, have made no effort to shake off the first surprise which my new conception of the dream evoked, and the professional philosophers, who are accustomed to treat the problem of dream life as a part of the states of consciousness, devoting to it a few—for the most part identical —sentences, have apparently failed to observe that in this field could be found all kinds of things which would inevitably lead to a thorough transformation of our psychological theories. The behaviour of the scientific critics could only justify the expectation that this work of mine was destined to be buried in oblivion; and the small troop of brave pupils who follow my leadership in the medical application of psychoanalysis, and also follow my example in analysing dreams in order to utilise these analyses in the treatment of neurotics, would not have exhausted the first edition of the book. I therefore feel indebted to that wider circle of intelligent seekers after truth whose co-operation has procured for me the invitation to take up anew, after nine years, the difficult and in so many respects fundamental work.
In the Preface to the First Edition, Freud indicates he is directing his work toward consideration of "neuro-pathological science" to examine "abnormal psychic formation." The Preface to the Second Edition, he states that his book was addressed to "the professional circles ... of [his] psychiatric colleagues." In the Preface to the Third Edition, he thanks his "other colleagues for their contributions and corrections." It is thus proven by these statements that Freud was writing for the scientific community of his psychiatric peers.
Whenever we think of audience, we need to consider factors such as the focus of the work and the style of language used. The fact that the arguments involve detailed knowledge of psychology indicates that this is not a book for people who do not have some knowledge of psychology.
The book was aimed at a scientific readership, which initially gave it a lukewarm reception. In fact, it only sold a few hundred copies. But it is important to note that over time, it gained a much broader readership. As Freud's fame spread, there was more of a popular demand for the book, which is why Freud published eight new editions over the next two decades. It is also important to note that he took the unique step of writing the book in the first person, and often in a narrative style, particularly in the parts where he describes his own dreams. So when you consider that his intended readership was initially the scientific community, the form he chose was highly unorthodox.
As the previous poster mentioned, Freud wasn't aiming to make the book a bestseller. One must keep in mind the company Freud was keeping and the people he knew would be interested in his work and these are not everyday working class people who are going to go out and pick up his book to read themselves to sleep at night. He was trying to reach and impress his colleagues and the people he worked with and those who had a direct interest in a discussion of dreams in an analytic context.
I would say that the audience is mostly other people involved in psychology. It's not exactly a book that is aimed at an audience of laypeople. I don't think you'd start with a literature review chapter if you're trying to go for a popular audience. So I'd say that this book is mostly aimed at other professionals in the field.
I would agree with both posters. I picked up the book during my Undergrad work and was completely confused by most of it. (My Undergrad minor is in Psychology.) While I have used it for specific ideologies, it is not a book that I would, or would have, read through. His text is certainly for professionals.