We describe an initial study into the identification of important and useful information units within documents retrieved by an information retrieval system in response to a user query created in response to an underlying information need. This study is part of a larger investigation of the exploitation of useful and important units from retrieved documents to generate rich document surrogates to improve user search experience. We report three user studies using a crowdsourcing platform, where participants were first asked to read an information need and contents of a relevant document and then to perform actions depending on the type of study: i) write important information units (WIIU), ii) highlight important information units (HIIU) and iii) assess importance of already highlighted information units (AIHIU). Further, we discuss a novel mechanism for measuring similarities between content annotations. We find majority agreement of about 0.489 and pairwise agreement of 0.340 among users annotation in the AIHIU study, and average cosine similarity of 0.50 and 0.57 between participant annotations and documents in the WIIU and HIIU studies respectively.