PDF exports of ArrayPlot's are fuzzy (OS X)

This is a problem with Preview, the PDF reader included in OS X. The problem does not show when using other PDF readers (not based on PDFKit) such as Adobe Reader.

To prevent blurring you just need to untick the "Smooth text and line art" checkbox under "Viewing documents" in Preview's preferences:

However, this will lower the quality of text and line art as well.

Actually, the problem is with Mathematica's export, at least with Version 10.

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

I have not found a setting in Mathematica to affect the value of this option on export to PDF.