PDFTron Annotations are disappearing

Product: PDFTron.UWP NuGet Package

Product Version:

Please give a brief summary of your issue:
PDF annotations disappear as more annotations are made.

Please describe your issue and provide steps to reproduce it:
One of our clients have come across an issue while using PDFTron where as they write, some previous annotations they have just made will disappear.

Just using our app, and using PDFTron to annotate a pdf, we find that, inconsistently, when writing numerical values exclusively 0s and 8s disappear.


Can you provide a sample project and PDF to reproduce this issue? I am not able to reproduce this issue, making it difficult to assist.

Perhaps the annotation’s bounding box is being cut off? As the user taps to write more, the annotation saves and applies to the PDF.


Thank you for the additional information, we will investigate when we can.

This is also something that I have come across in the PDFTron UWP Demo Sample provided by PDFTron on Github:

PDFTron/pdftron-uwp-samples (github.com)

Thus it is most likely a PDFTron issue. It would be great to have this investigated as soon as possible.

Issue recreated:

Hi derek/PDFtron Team,

Is there any update for this issue?

Hi saad,

The reported issue is difficult to reproduce, it seems to happen when there are limited resources and the annotation fails to save before the next annotation is started. I suggest disabling continuous annotation setting instead of generating many annotations by pen strokes.

How can this be set? I have tried looking and have not managed to find it, either on the API or in the code.

Hi saad,

You could try a combination of toggling the property pdftron.PDF.Tools.Controls.Viewer.ViewerSettings.ButtonsStayDown = false; and changing the timer between pen strokes to pdftron.PDF.Tools.Controls.Viewer.ViewerSettings.TimeBetweenPenStrokesMilliseconds = 5000;.

Hi derek,

Unfortunately I do not this these settings are useful for us.

Unsure of setting TimeBetweenPenStrokesMilliseconds’s effect alone, but bug still occurs (tested on desktop dev build as it’s easier to reproduce bug).
But setting ButtonsStayDown to false just means that without using stylus, any tool selected from toolbar is only going to be able to be used once before you need to press on the tool again.
This is redundant with stylus, as you can write as much as you want still.
And thus, the assumption that on a device with a stylus (all of our devices), the issue still would exist.