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Document Viewer


Document Viewer components

PDFViewCtrlReflowFloating context menuCustomize floating context menuAnnotation toolbarAnnotation style editorCustomize annotation style editorPage sliderAnnotation listDocument outlineUser bookmark listList containerThumbnail browserAdd pages dialogRotate pages dialogView mode dialogCrop pages dialog

Annotation and collaboration

OverviewToolManager setupRead only modeDisable annotation creation/editingDefault annotation propertiesAnnotation propertiesEventsOverride annotation handlingShow and hide existing annotationsUndo and redoRealtime collaboration

Advanced customization

Add a custom view to a pageCreate a custom toolPage coloring modePage fit modePage layout mode


Convert documents to PDFConvert HTML to PDF


Text search

Other Frameworks


Advanced topics

Understand coordinatesDocument savingDocument lockingGenerate page thumbnailsTool class hierarchy


System RequirementsRun project in Android StudioRun project with source codePDFTron full vs. standardLocalizationIcon cheat sheetReduce size of APKEnable multidexOut of memory when rotating device multiple timesReduce memory consumptionDetachCurrentThread warning

PDF Processing API

What is PDFNet?Opening a documentSerializing (saving) a documentWorking with pagesWorking with Page ContentWorking with BookmarksWorking with Interactive Forms (AcroForms)PDF SecurityLow-level PDF APIError handling
Realtime collaborationkeyboard_arrow_down

Realtime collaboration

In this document
chevron_rightInitializing and sending annotation changes
chevron_rightReceiving annotation changes
chevron_rightJump to annotation

PDFNet supports annotation syncing between different clients to allow for collaboration. All the required locking, change tracking, merging and view updating are handled internally. Below are instructions on how to handle the import and export of annotation changes on the client side. While the server component is not described here, that implementation would be straightforward. The server would receive XFDF XML data, which it would then pass onto all other active clients that are part of the collaboration session. The clients take care of the updating. The server can store any XFDF data as it likes, since the data is just an XML string.


Here are a few requirements for syncing to work as expected:

  • A permanent and unique string identifier is needed for the userId. UserId needs to be permanent and cannot be changed later on. For example, if Alice was used for the userId, however, was later changed to AliceB, the viewer will no longer treat it as the same user. Therefore, we recommend that you generate a UUID for each user.
  • Similar to userId, each annotation will also need its own UUID, aka annotId. This UUID also needs to be permanent and unique.
  • Annotation changes are stored as XFDF command strings, which PDFNet generates when changes are made. However, any custom modification to the XFDF command string could lead to unexpected results, thus, modification to the XFDF command string are not recommended.
  • Existing annotations that do not have a unique identifier will not work, it is recommended that you pre-process all annotations to make sure they all have unique identifiers.
  • Undo and redo will be automatically enabled upon using annotation syncing.

linkInitializing and sending annotation changes

Add the following after ToolManager is initialized:

PDFNet will generate a unique identifier for every annotation created through the PDFTron SDK. However, if you would like to generate your own annotation identification, you are able to do so as follows:

linkReceiving annotation changes

When an annotation change event is received from a remote service, add the following to notify the viewer about the change:

linkJump to annotation

To jump to an annotation by id: