Unable to update file Report.xlsx. The file size of the Document to Update is at least 100 times larger when uncompressed, which constitutes a security risk.

You mention that your file is less than 4 gigabytes for 500 rows. What kind of file is this? Why do 500 rows use that much space?

sorry i mentioned it cause i read  the documentation of this  smart service there says that this  could be  two main reasons why this error is thrown and  i wanted to  skip that talk about those posibilities.the    file is just 101 kb

What's the difference in size compressed vs uncompressed? Have you checked the tomcat-stdout log to see if there is any additional information there?

I have a similar problem where the attachment file is only 70kb but it gives this error. Do we have a solution for it yet? Thank you

i changed my document cause it had  too much  repeated information  and i  wasn´t able to see the tomcat-stdout log  in myappian  portal cause i don't have access to it. if you have access to it you could  see aditional information there about  this problem and post it  here to see if   someone give us more info   about this. cause i'm pretty sure i will get this  error again  sooner than later again.

I found this and I now have some more insights into how I can fix this error: 
KB-1708 Errors related to file size thrown when using the Export to Excel/CSV smart service - Appian Knowledge Base - Support - Appian Community

It's true that my download has a lot of repetitive cell values. I'm trying to fix it, hoping this will work out. 

FIXED! 

I simply removed the older file (70kb, 15 rows) and uploaded a new base file (with only headers, size: 10kb) and referenced to new file. Since the new file is all blank with only headers, repetitions shouldn't happen again. I believe that the older file caused error since the table I was querying has a lot of test data and tons of repetitions (say my name as Process Owner). Seems like this wouldn't usually occur in production/real data.