A similar problem is being discussed in this thread. I'll copy my method of going around it here, in case someone stumbles on this thread through searches.

I have been saving a file wit MatrixPlot (using Save As...-> PDF), and have encountered a similar problem.

Turns out, MatrixPlot (and similar) data is being exported as a bitmap, which gets blurred in Adobe Reader 9 (which I have), even if "Smooth line art" and "Smooth images" is unchecked in preferences. The PDF showed fine in Okular, but that is probably just the lack of smoothing in that viewer.

I have found the solution on Inkscape forums. Open the PDF file in a text editor, and locate the following line:

/Interpolate true

Change it to the following:

/Interpolate false

Et voilà! The problem is solved, and the PDF shows fine in Adobe Reader, without blurring.

A similar problem is being discussed in this thread. I'll copy my method of going around it here, in case someone stumbles on this thread through searches.

I have been saving a file wit MatrixPlot (using Save As...-> PDF), and have encountered a similar problem.

Turns out, MatrixPlot (and similar) data is being exported as a bitmap, which gets blurred in Adobe Reader 9 (which I have), even if "Smooth line art" and "Smooth images" is unchecked in preferences. The PDF showed fine in Okular, but that is probably just the lack of smoothing in that viewer.

I have found the solution on Inkscape forums. Open the PDF file in a text editor, and locate the following line:

/Interpolate true

Change it to the following:

/Interpolate false

Et voilà! The problem is solved, and the PDF shows fine in Adobe Reader, without blurring.