By default, iCS for PDF does not perform attribute exchange inside references, to avoid problems with concurrent extractors. Best practice is for title blocks to be in the master DGN.
In case you still need this to work, manual entry in Orchestration Framework Database for below parameter needs to be made. Orchestration Framework service should be restarted in order for this change to be read.
For CE Up 3 and earlier - Add a row to the "rendsvcIplotConfiguration" table with Name="PW_TITLEBLOCKS_SKIP_TAGS_IN_REFERENCES", no value.
For CE Up 3.1 later builds - Add row in table "rendsvcConfiguration" with Name="UpdateTitleblocksInReferences", value "1"
Be advised that there is good reason this is not the default behavior. Assuming multiple rendition processors, which is frequently the case, If the reference is shared between multiple master files, and those master files and all of their reference files are opened simultaneously for read/write (required for attr exchange to work), then only the first processor will successfully open the reference in question with write access. The other processor(s) will be given read-only access to that reference, and attribute exchange will silently fail. Thus, reference attribute exchange cannot be completely relied upon in a multi-rendition-processor deployment, and thus should be used with caution. Best practice is put title blocks in the master file, which is guaranteed to be locked by only one process at a time.