Trying to create an array of filenames - powershell

Question

I am trying to use the PSWritePDF module to merge pdfs. I have about 64 folders and each of them have about 20+ files that need to be merged. In the end, I would have 64 pdfs, each containing the merged files from each of the 64 folders. I have already written some code but I am struggling to create an array of file names that I can pass to the Merge-PDF function. I know the first part of this code is redundant, just haven't fixed it yet.
#https://github.com/EvotecIT/PSWritePDF/blob/master/Example/Example03.Merging/Example03.ps1
#This gives me the 64 folder names
$folder_NM = Get-ChildItem -Path \\main_directory\CURRENT |
Where-Object {$_.PSIsContainer} |
Foreach-Object {$_.Name}
#This iterates through the 64 folders
foreach ($X IN $folder_NM)
{
#this grabs each of the 64 directories
$main_path = join-path -path \\main_directory\CURRENT -ChildPath $X
#This grabs the names of the pdfs in each folder
$file_names = Get-ChildItem $main_path |
ForEach-Object {$_.Name}
#This is grabbing each file in the folder and giving me the formatted string I need to pass to Merge-PDF. i.e. C:\\User\Current\pdf.1
foreach($Y in $file_names){
$idv_files = join-path -path $main_path -ChildPath $Y
#This is where I am stuck. I am trying to create an array with each filename comma separated. This currently just overwrites itself each time it goes through the loop.
$arr = $idv_files-join','
#This is needed for mergePDF
$OutputFile = "$maindirectory\TESTING\$X.pdf"
#This only puts the most recent file in the output file. Thus the need for an array of file names.
Merge-PDF -InputFile $arr -OutputFile $OutputFile
#Debugging
#Write-Host $arr
}
}
Specifically, this is where I am struggling. I am getting the correct files in $idv_files and if I use those in Merge-PDF then I just get a PDF with the one file that was processed last. I think I just need them comma separated and all put into the same array so that Merge-PDF will merge them all together.
foreach($Y in $file_names){
$idv_files = join-path -path $main_path -ChildPath $Y
#This is where I am stuck. I am trying to create an array with each filename comma separated. This currently just overwrites itself each time it goes through the loop.
$arr = $idv_files-join','
Anything helps. Very new to powershell!

Answer 1

Untested but, if the function takes [string[]] as input as in my comment, this should get you a MERGED PDF.pdf on each folder.
I would recommend you to test this with a few folders containing pdf files on your local host before trying with your FS.
# Get the Directories
$folder_NM = Get-ChildItem -Path \\main_directory\CURRENT -Directory
#This iterates through the 64 folders
foreach ($dir IN $folder_NM)
{
# This gets you the array of PDF Files
$file_names = Get-ChildItem $dir.FullName -Filter *.pdf -File |
Sort-Object Name
# Define the output file for Merged PDF
$OutputFile = Join-Path $dir.FullName -ChildPath 'MERGED PDF.pdf'
# If Merge-PDF takes [string[]] as input, this should work
Merge-PDF -InputFile $file_names.FullName -OutputFile $OutputFile
}

Answer 2

It appeared that you wanted the merged .pdf file to be the subdirectory name + '.pdf'. Perhaps I misunderstood. This is also UNTESTED, but might do what you want. Using the current Windows PowerShell 5.1 or any PowerShell Core, testing for .PSIsContainer is not necessary. Get-ChildItem supports -File and -Directory switches.
[CmdletBinding()]
param ()
$RootDir = '\\main_directory\CURRENT'
# Get the subdirectory list.
Get-ChildItem -Directory -Path $RootDir |
# Process each subdirectory.
ForEach-Item {
# Create an array of the .pdf files to be merged.
$file_names = (Get-ChildItem -File -Path $_.FullName -Filter '*.pdf').FullName
#This is needed for mergePDF
$OutputFile = Join-Path -Path $RootDir -ChildPath $($_.Name + '.pdf')
Write-Verbose "OutputFile is $OutputFile"
Merge-PDF -InputFile $file_names -OutputFile $OutputFile
}