Need a responsive full page (Bootstrap) or web part
Pulls filtered data from Workflow Tasks
Looks up tasks Related Items from doc. lib. and displays a subset of properties and the pdf doc
Must display the full pdf with zoom & paging
Allow the user to approve/reject the workflow task with comments (required for reject) on same page
Allow user to edit the related item properties on same page
Please specify the stack you are recommending e.g. SP Add-in or SPFx Web Part or something else.