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Currently the theme for submission pdfs depends on where the last activity activity is submitted. For Example, If the first activity in a flow is submitted from a space with the Nouveau Blue theme and the second activity is performed directly from a Task List outside the space, the submission PDF renders in the Nouveau theme which is the default theme that for the Task List uses. If the last activity in a flow is submitted from a space, the submission pdf renders in the space's theme.
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