Additional information:
premise:
p1) I made a test changing the owner and group of the /tmp/at-spi2/ folder with the user logged-in solve the problem. Maybe it was granted, but it tried anyway
p2) Evince seem to work fine, I never detected problems reading pdf file during normal work. This error does not seem to affect the entire program operation. 

Based on of my knowledge I have tried to verify the requirements requested by Jamie Strandboge:
a1) the environment and /tmp/at-spi2/:
considering what I have discovered a way to change the environment connected to the '/tmp/at-spi2/' is to define XDG_RUNTIME_DIR, but this variable is not defined,  the command env|grep XDG produce:
  XDG_SESSION_COOKIE=023e99a7ae9aa1d1d49fde2300000008-1393614529.236409-511883369
  XDG_CONFIG_DIRS=/etc/xdg/xdg-gnome-shell:/etc/xdg
  XDG_DATA_DIRS=/usr/share/gnome-shell:/usr/share/gnome:/usr/local/share/:/usr/share/
  XDG_CURRENT_DESKTOP=GNOME
This is certainly not exhaustive but that's what I was able to discover about this

a2) why is evince trying to chmod it?
I don't know the internal reasons of evince but this operation is always done even when it is launched from the command without opening a pdf file directly. I made an strace of evince launch from commnad line, a simple evince, and these are the interesting lines:
...
  recvmsg(11, 0x7fff3dbbb490, MSG_CMSG_CLOEXEC) = -1 EAGAIN (Resource temporarily unavailable)
  eventfd2(0, O_NONBLOCK|O_CLOEXEC)       = 12
  write(12, "\1\0\0\0\0\0\0\0", 8)        = 8
  fstat(11, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0
  fcntl(11, F_GETFL)                      = 0x802 (flags O_RDWR|O_NONBLOCK)
  write(4, "\1\0\0\0\0\0\0\0", 8)         = 8
  brk(0x7f6836ff0000)                     = 0x7f6836ff0000
  brk(0x7f6836fef000)                     = 0x7f6836fef000
  sendmsg(11, {msg_name(0)=NULL, msg_iov(2)=[{"l\1\1\1Y\0\0\0\2\0\0\0\177\0\0\0\1\1o\0\25\0\0\0/org/fre"..., 144}, {"T\0\0\0type='signal', interface='or"..., 89}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 233
  sendmsg(11, {msg_name(0)=NULL, msg_iov(2)=[{"l\1\1\1d\0\0\0\3\0\0\0\177\0\0\0\1\1o\0\25\0\0\0/org/fre"..., 144}, {"_\0\0\0type='signal', interface='or"..., 100}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 244
  sendmsg(11, {msg_name(0)=NULL, msg_iov(2)=[{"l\1\0\0010\0\0\0\4\0\0\0\202\0\0\0\1\1o\0\37\0\0\0/org/a11"..., 152}, {"\5\0\0\0:1.38\0\0\0\37\0\0\0/org/a11y/atspi/"..., 48}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 200
* mkdir("/tmp/at-spi2/", 01777)           = -1 EEXIST (File exists)
* chmod("/tmp/at-spi2/", 01777)           = -1 EACCES (Permission denied)
  socket(PF_FILE, SOCK_STREAM|SOCK_CLOEXEC, 0) = 13
* stat("/tmp/at-spi2/socket-4587-1804289383", 0x7fff3dbbb550) = -1 ENOENT (No such file or directory)
  setsockopt(13, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
* bind(13, {sa_family=AF_FILE, path="/tmp/at-spi2/socket-4587-1804289383"}, 37) = 0
  listen(13, 30)                          = 0
  fcntl(13, F_GETFL)                      = 0x2 (flags O_RDWR)
  fcntl(13, F_SETFL, O_RDWR|O_NONBLOCK)   = 0
* chmod("/tmp/at-spi2/socket-4587-1804289383", 0777) = 0
  open("/dev/urandom", O_RDONLY)          = 14
  read(14, "\320\262\323\266\243\246\206\214\331G\v\330", 12) = 12
  close(14)                               = 0
  fstat(13, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0
  fcntl(13, F_GETFL)                      = 0x802 (flags O_RDWR|O_NONBLOCK)
  write(4, "\1\0\0\0\0\0\0\0", 8)         = 8
  openat(AT_FDCWD, "/usr/lib/evince/4/backends", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 14
  getdents(14, /* 14 entries */, 32768)   = 584
  open("/usr/lib/evince/4/backends/dvidocument.evince-backend", O_RDONLY) = 15
...

only five lines marked with '*' contain a reference to /tmp/at-spi2 folder

That's all for now.

No one else who follows this bug has been dealing with a similar problem?

Many thanks to all !!!