$ emerge -tuD world
These are the packages that I would merge, in reverse order:

Calculating world dependencies  ..... ..... . ...done!
[blocks B     ] app-text/poppler (is blocking app-text/pdftohtml-0.36-r4)
[nomerge      ] app-cdr/k3b-0.12.8  
[nomerge      ]  media-video/transcode-0.6.14-r3  
[nomerge      ]   media-libs/netpbm-10.30-r1  
[ebuild     U ]    media-libs/jbigkit-1.6-r1 [1.4] 
[ebuild     U ] sys-process/psmisc-21.9 [21.6] 
[nomerge      ] net-zope/plone-2.1  
[nomerge      ]  net-zope/archetypes-1.3.4  
[nomerge      ]   net-zope/portaltransforms-1.3.7  
[ebuild  N    ]    app-text/pdftohtml-0.36-r4  
[nomerge      ] net-fs/samba-3.0.14a-r2  
[nomerge      ]  dev-libs/popt-1.7-r1  
[ebuild  N    ]     net-print/cups-1.1.23-r7  
[ebuild  N    ]      app-text/poppler-0.4.3-r4  


$ emerge -Dvup
These are the packages that I would merge, in order:

Calculating world dependencies  ..... ..... . ...done!
[blocks B     ] app-text/poppler (is blocking app-text/pdftohtml-0.36-r4)
[ebuild  N    ] app-text/poppler-0.4.3-r4  -cairo +jpeg +zlib 0 kB 
[ebuild  N    ] net-print/cups-1.1.23-r7  +cjk -gnutls +nls +pam +samba +slp +ssl 0 kB 
[ebuild  N    ] app-text/pdftohtml-0.36-r4  0 kB 
[ebuild     U ] sys-process/psmisc-21.9 [21.6] +ipv6 +nls (-selinux) 0 kB 
[ebuild     U ] media-libs/jbigkit-1.6-r1 [1.4] 0 kB 

Total size of downloads: 0 kB