Localization, document import, and annotation improvements:
- The interface is now available in Spanish, French, German, and Brazilian Portuguese — follows your system language, or pick one under View → Language.
- Import Word (.docx), Excel (.xlsx), CSV, plain text, and Markdown files without any external programs — the Flatpak can now import these formats too.
- Merge accepts a single file, so one image or document can be converted to PDF directly.
- Import a signature from an image file via the new Upload tab (transparent PNGs work best).
- Custom stamps now persist across restarts, with a "Your Stamps" section in the picker; added a red PAID stamp.
- Drag with the Text tool to size the box before typing.
- File dialogs remember the last-used folder (non-Flatpak).
- Fixed Greek and math symbols (Δ, λ, ≈, ...) failing with "WinAnsi cannot encode" when saving, flattening, or printing — a Unicode font subset is embedded automatically.
- Fixed text boxes on rotated pages: vertical-sliver editing box, resize handles affecting the wrong edge, and saved output not matching the screen.
