It is possible to implement this feature (e.g. text edit with reflow etc) using PDFNet but it is not trivial. PDF formats is a fixed format and is not designed to support editing, versus Word documents which do but don’t guarantee visual integrity over time and over different applications.
Please look at the following related forum postings:
https://groups.google.com/forum/?fromgroups=#!topicsearchin/pdfnet-sdk/group:pdfnet-sdk$20AND$20reflow/pdfnet-sdk/wP9eLb6xMtQ
https://groups.google.com/forum/?fromgroups=#!topicsearchin/pdfnet-sdk/group:pdfnet-sdk$20AND$20reflow/pdfnet-sdk/4yJNs0_Ne38
If you are dealing with PDF templates you could edit text (search & replace) using ContentRelacer as shown in ContentRelacer sample:
http://www.pdftron.com/pdfnet/samplecode/ContentReplacerTest.cs