pdfflip: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/pdfflip - from package: pdfjam

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/pdfflip - from package: texlive-extra-utils

You may install the required package with command apt-get install {package}

Error in other languages:
pdfflip: bevel nie gevind nie
pdfflip: comandă negăsită
pdfflip: comando não encontrado
pdfflip: commande introuvable
pdfflip: command not found
pdfflip: käsku ei ole
pdfflip: không tìm thấy lệnh
pdfflip: komanda nerasta
pdfflip: Kommando nicht gefunden.
pdfflip: kommandot finns inte
pdfflip: komut yok
pdfflip: nie znaleziono polecenia
pdfflip: níor aimsíodh an t-ordú
pdfflip: no se encontró la orden
pdfflip: no s'ha trobat l'ordre
pdfflip: opdracht niet gevonden
pdfflip: parancs nem található
pdfflip: perintah tidak ditemukan
pdfflip: príkaz nenájdený
pdfflip: příkaz nenalezen
pdfflip: команда не найдена
pdfflip: командата не е открита
pdfflip: 命令找不到
pdfflip: コマンドが見つかりません