History module

The History module shows the timeline of the changes applied to your document since it was opened, and lets you preview or restore an earlier step. It is a local backup at document level: at each significant operation (rotation, watermark, merge, compression, and so on), HtkPDF creates a checkpoint that can be restored as long as the document is open. You reach this module from the General category of the Dashboard.

Automatic creation of checkpoints

You do not have to trigger the recording of a checkpoint: HtkPDF creates one automatically every time a module confirms an operation on the document. This includes in particular:

Pages: merge, split (note: splitting does not alter the current document), extraction, deletion, reordering, rotation, cropping, resizing, deletion of blank pages, insertion of a blank page, reversal, import through Continuity Camera;
Annotations and markings: watermark (text or image), Bates numbering, highlighting, notes, shapes, stamps, drawings, hyperlinks, redaction, signatures;
Forms: adding, changing or deleting a field;
Metadata: changing a field, complete scrubbing;
Security: configuring password protection, unlocking;
Conversion / optimization: flattening, compression, greyscale;
Outline: applying a new table of contents.

The initial checkpoint is the document as you opened it. Every subsequent change attaches to it in sequence.

The chronological interface

The History is presented as a vertical timeline, with the oldest steps at the top and the most recent at the bottom. Each entry shows:

a colored dot in the left margin, joined to its neighbours by a continuous line. The dot currently active (the last one applied or previewed) appears highlighted;
an icon recalling the type of operation (a pencil for a generic edit, scissors for a split, and so on);
the name of the action (for example "Watermark", "Compression", "Rotation");
the time at which the operation was performed;
a Restore button to bring the document back to that version;
a View button to preview without restoring.

When the module opens, the list automatically scrolls to the most recent step.

Previewing a version

Clicking View (or the row itself) loads the corresponding version into the PDF view on the left, without marking the document as modified. That lets you quickly compare two steps or check a specific change without committing.

The View button of the active row is greyed out to indicate that it is the version currently displayed.

Restoring a version

Clicking Restore brings the document back to the corresponding state and triggers the pending changes state:

the restored version becomes the working copy;
the Save button on the Dashboard becomes active again;
any pending security option (protection configured but not yet saved) is cleared — protections are not kept in the checkpoints.

⚠️ Restoring does not delete the later checkpoints: they stay available in the list, and you can "redo" more recent steps by clicking their Restore button. This is more permissive than a classic undo: you can jump from one step to another freely.

Persistence and limits

The history is local to the current session: it is lost when you close the document. It is not written into the PDF file.
Nor is the history shared between several windows: each opening of the same file builds its own history from the document's initial state.
To keep a durable record of the intermediate steps, save each important version under a different name (for example myfile_v1.pdf, myfile_v2.pdf). The internal history is no substitute for good version management on disk.

Restoring from a specific module

Several editing modules also have their own Undo and Redo buttons in the header of their sidebar. These buttons act at a fine level (undoing the last annotation action, for example), whereas the global History acts at module level (going back to before the Watermark module was opened, for example).

For granular operations while editing within a module, use that module's Undo / Redo buttons. To go back several steps, use the global History.

Best practices

Before a risky operation (deleting pages, flattening, scrubbing metadata), a checkpoint is generated automatically at the preceding step. Check its name in the history before proceeding;
Combine with regular saving: checkpoints are only kept within the current session. For major changes, save the PDF between two steps so you can physically go back even after closing;
Clean the history regularly: there is no button to empty the session history, but once the document has been closed and reopened, the list starts empty again.

Screenshots

1 screenshot — click to enlarge