OmniFocus 2.19 introduces a new attachment storage and sync system. To migrate to the new system you’ll need to be running OmniFocus 2.19 or later on all of your iOS devices and OmniFocus 2.9 or later on all of your Macs. Once all of your syncing devices are running a version that supports the new system, you’ll be prompted to migrate your database.

• Attachments — Starting with v2.19 (iOS) and 2.9 (Mac), OmniFocus stores attachments separately from the items that contain them, resulting in improved performance and storage efficiency. Once all of your syncing devices are running a version that supports the new attachments, you’ll be prompted to migrate your database.
• Attachments List — A new Attachments row is availabe in Settings, where you can view all of your attachments in the same place (sorted by date added or size), quickly get to the item(s) that reference them, and remove attachments you no longer need.
• Sync — OmniFocus now handles the DAV 207 multi-status responses returned by NGINX in its default configuration with the nginx-extras APT package.
• Device List — Added information to the list in Sync Settings to make it easier to tell which of your devices are connected.
• Encryption — We now offer to immediately re-upload and re-encrypt your database when you change your encryption passphrase.
• Settings — Added a > to the Clean Database row (this row is visible only when your database contains a large number of completed items) so that it’s clearer that another screen will tell you what the feature actually does.
• Localizations — Updated Localizations.

OmniFocus 2.18.2 fixes bugs and adds awareness of a change to the way we handle attachments (coming in v2.19).

• Repeating Items — Fixed a problem where a slow connection to your sync location could cause a long delay between checking off a repeating item and the next iteration’s appearance.
• Today Widget — Fixed a widget crash that would result in “Unable to load” being displayed.
• Crashes — Fixed a crash related to Reminders Capture, among others.
• TaskPaper — Fixed a regression pasting TaskPaper text where the values of @autodone or @parallel were ignored when present.
• Future File Formats — Updated OmniFocus’ “capabilities” system to provide more helpful errors when an un-parseable database is encountered.