So I created a batch task that loops through all the segments in an sdlxliff file.

Here is some example code:

The Task:

    public class TranslateTask : AbstractFileContentProcessingAutomaticTask
    {
        protected override void ConfigureConverter(ProjectFile projectFile, IMultiFileConverter multiFileConverter)
        {
		multiFileConverter.AddBilingualProcessor(new SegmentProcessor());
        }
    }

The Processor:

public class SegmentProcessor : AbstractBilingualContentProcessor
{
	public override void ProcessParagraphUnit(IParagraphUnit paragraphUnit)
	{
	    if (paragraphUnit.IsStructure)
	    {
	        return;
	    }

	    foreach (var segmentPair in paragraphUnit.SegmentPairs)
	    {
	        if (IgnoreSegment(segmentPair))
	        {
	            continue;
	        }

                // The following code DOES NOT WORK. Casting to Itext return null.
                foreach (var target in segmentPair.Target)
                {
                    var text = target as IText;
                    if (text != null)
                    {
                        text.Properties.Text = "Updated";
                    }
                }
	    }
	}
}

Question:

Is there a simple way to update the Target text in each segment pair?

If there isn't. What do I need to do to accomplish this?