JP is right, putting the employees into an array is the fastest way to do it, but judging by the title of your post, you need help with looping. As the old saw goes, "get it working, get it working right, get it working fast." Let's focus on step one for now.
So here's a spreadsheet I called "Employees":
Employee Num Last name First name
1 Smith John
2 Jablomi Heywood
3 Meoff Jack
And since it sounds like you've gotten it working where you manually enter an employee number into a cell, we'll work with that model for now as well. So what we'll do is loop through all the employees, entering each employee number into cell A5 of your "payslip" sheet, then call whatever sub you have that does the email and pdf.
My suggestion is to create a new workbook, name one sheet "Employees" and add the previous data list to it, another sheet "payslip", go into the VBA editor and add a new module, then paste this code:
Public TotalEmployees As Integer
Public Sub LoopThruEmployess()
'this is the variable for looping
Dim i As Integer
'this is where you're now manually entering the data (setting a variable for the range will speed up the program)
Dim Target As Range
Set Target = Sheets("payslip").Range("a5")
'This is the Source Row from which the "Offset" function will work
Dim SourceRow As Range
Set SourceRow = Sheets("Employees").Range("A1")
'Note that this assumes two things:
'One, that you have no text in any cells in the "A" column besides the header column,
'and two, that your header column is in row 1
'The " -1 " accounts for the header row
TotalEmployees = WorksheetFunction.CountA(Sheets("Employees").Range("A:A")) - 1
'I use a For loop because it's faster than testing each row as you go down the column, though as JP said, it's faster to copy the range to an array (almost 50 times faster)
'The " i = 1 " accounts for the list of employees starting in row 2
For i = 1 To TotalEmployees
Target = SourceRow.Offset(i, 0)
MsgBox "Call your Subroutine that emails, pdf's your payroll slip for employee number " & Target & " here"
I just tested it to make sure there's no typos, so it should work fine. Once you're comfortable with how it works, incorporate it into your existing solution.
Hope that helps,