Proposed roadmap as milestones

Milestone 1 — “Fast Preview & Thumbnails”
Outcome: current app feels responsive.

- delete PageList
Version
fix thumbnail sizing
progressive thumbnail rendering - Thumbnail generation: show already when not done completely; cache
thumbnail cache
preview next/previous - Flip through preview; tools on preview
keyboard shortcuts for preview and selection - Keyboard shortcuts (Ctrl+A, Del, arrows to navigate pages, etc.)
README update for current feature set - README

Milestone 2 — “Real Page Workspace”
Outcome: pages become editable workspace objects, not just indices.

introduce PageRef
duplicate selected pages - “Duplicate selected pages” into a new position
extract selection as new workspace - “Extract selection as new workspace” (open selection as a separate working document)
command history model
A sidebar history/command log
undo/redo - Undo / Redo
grid/list toggle - A grid/list view toggle

Milestone 3 — “Better Merge & Mobile”
Outcome: multi-document workflows become natural.

full multi-file merge queue - Full multi-file merge UI (queue merges, reorder incoming files)
drag PDF into page grid at hovered position - Support for drag-drop PDF into page grid to merge at the hovered position
long-press drag on mobile - Long-press drag on mobile (custom touch-DnD)
improved toolbar - UI toolbar
mobile layout cleanup - Mobile

Milestone 4 — “Structural PDF Editing”
Outcome: support common non-content-stream PDF edits.

metadata editor - Metadata editing
crop pages - Crop pages?
preview tools
form read/fill/flatten - Form read/fill/flatten
bookmarks read/edit, probably read first - Bookmarks editing
annotations read, write later - Annotations read (write optional)

Milestone 5 — “Export, Extraction & Power Tools”
Outcome: stronger output workflows.

basic text extraction - Basic text extract
optimize/compress MVP
Optimize & compress PDF
encrypted PDF handling, carefully scoped - Encryption / Decryption
ZIP export for split results
versioning/release polish