title: panel.border in ggplot2 ploting thicker lines in bottom and right side of the plot in CairoPDF device
body: <p><img src="https://i.stack.imgur.com/UBF31.png" alt="enter image description here"></p>
  
  <p>I am using Cairo setting as</p>
  
  <pre><code>CairoPDF(file = "test2.pdf", width = 8.3, height = 11.7) 
  </code></pre>
  
  <p>and theme setting is like this:</p>
  
  <pre><code>mytheme&lt;-theme_bw() +
           theme(plot.title = element_text(lineheight=.8, face="bold"),
                 text=element_text(size=11, family="Times New Roman"))+ 
           theme(panel.border = element_rect(linetype = "dashed", 
                                             colour = "black"))+ 
           theme(plot.margin = unit(c(1,1.5,1,1.5), "inches"))
  </code></pre>
  
  <p>I guess, this is a problem with my theme setting for ggplot. please give advice to fix it. 
  Thanks.</p>